Without question, this is, by far, the best account for non-specialists of how genes influence behaviour. I would add that most genetics specialists will also learn a good deal from it. The authors gave themselves the task of making the book ‘accurate, accessible, self-critical, and (above all) entertaining’ (p. 3). They have succeeded in spectacular fashion in achieving that rather ambitious goal. There are other excellent popular accounts of genetics, and especially of gene–environment interplay, but this book covers a much broader range of issues. It is distinctive in having three authors who are international leaders in three rather different areas – human studies, rodent studies, and the genetics of fruit flies, but all three authors have both a broader vision of what genetics is all about and experience in several different branches of genetic research. The tone of the book is rightly positive about the contributions of genetics (both achieved and potential), but it is realistic about the achievements so far. Thus, they conclude that the discoveries in relation to schizophrenia ‘have not yet provided unambiguous answers to questions about the cause of the disorder’ (p. 4).

So what does the book cover? First, it provides a particularly clear description of what is involved in the different types of genetics. This is combined with an interesting discussion of the ways in which some of the iconoclastic creative pioneers in these fields challenged the ‘given wisdom’ of the day and, in so doing, provided important ‘breakthroughs’ in understanding. Readers will gain an appreciation of how the best scientists thought about the issues and worked out how to take the science forward. Finally, the authors pull together the key substantive findings in order to draw conclusions on what these mean for both theory and practice.

The book outlines in a very readable style what is special about quantitative human genetics, (covering twin, family and adoptee studies); molecular genetics (explaining the differences between linkage analysis and association studies); rodent genetics (involving mapping and cloning genes, based on multigenerational inbreeding between sibling pairs and re-combinations); chromosome studies that may point to possible genes worth more detailed study; flies and worms (which allow the study of much simpler neural systems), and experimental interventions that would not be allowed in higher organisms; model systems (such as those involving circadian rhythm or geotaxis by altering genes in order to determine the behavioural consequences that allow study of mechanisms at the molecular level); and basic neuroscience/neurobiology.

It is made clear that quantitative genetics is concerned with genetic and environmental influences on individual differences in natural populations, whereas animal models are concerned with experimentally induced mutations. They tackle quite different questions and it should not, therefore, be surprising that sometimes they seem to give contradictory answers. Cautions are expressed about what can and cannot be concluded from gene knock-outs. They draw an analogy with a hypothetical experiment in which the main cable controlling the wing flaps on planes is cut, thereby making flight impossible. But that would not mean that the cable provided the basic cause of flying, although it did deal with a crucial component.

The book notes the fact that the effects of major genes are often altered by variations in the genetic background – implying a synergistic interaction between genes (so-called epistasis). Behavioural geneticists are often puzzled by the apparent contradiction between this conclusion from animal models and the consistent evidence from human quantitative genetics that most genetic effects are independently additive and not synergistic. Perhaps the answer might lie in the fact that, for the most part, the animal models are dealing with rare pathogenic mutations of single genes, whereas the human studies are dealing with common, normal, allelic variations. The authors have all the skills needed to discuss gene–gene synergism in a critical way and it is a pity they did not take on this topic.

The important recent discovery of sub-microscopic copy number variations (CNVs) is rightly highlighted with respect to their likely causal role in relation to both autism and schizophrenia. Unfortunately, however, their meaning is not critically examined. Thus, why are CNVs more common in both these conditions compared to the general population? Should they be viewed, for example, as developmental perturbations arising from stochastic (chance) factors (such as provided by raised parental age)? The same query arises with respect to the raised rate of chromosomal anomalies and minor congenital anomalies in autism. Overall, the account of neuroscience neglects the important role of chance. It is well established that the original programming of brain development is probabilistic – making it necessary for neuronal pruning, to ‘fine tune’ the structure and functions to produce a well-functioning brain. How might this be relevant with respect to genetic influences?

Attention is appropriately drawn to the new findings on rare single major genes (especially in relation to autism) but how far are the findings generalizable to the overall population of individuals with autism? If many of the genes (or the CNVs) do not run in families, how can they explain the observed familiality of autism? Also, if the specific CNVs are not the same in different families (as seems to be the case), what might this mean? Could the rare gene findings help to explain the puzzle that although individuals with either autism or schizophrenia show a markedly reduced fecundity, neither condition has died out? If there is markedly reduced inter-generational transmission, why has it not been eliminated? Do the findings on the broader phenotypes of both conditions help and, if not, why not? It is a pity that the authors chose to side-step these major questions. The book clearly deserves to go into a second edition and, perhaps, especially as very little in the book needs changing, the authors might be persuaded to rise to these other challenges (as well as correcting the misspelling of Ronald Fisher's name).

The book is generally fair on the controversial issues – such as gene–environment interaction (G×E) and genome-wide association studies (GWAS). With respect to G×E, they argue that it should be expected to occur but questions need to be raised about specific findings. With respect to GWAS, they note its potential for identifying novel genes but critics could rightly claim that they had rather a rush of blood to their heads in arguing for the major achievements of GWAS. Obviously, it constitutes an important strategy but, since this book was written, doubts have been expressed on the meagre achievements of GWAS especially with respect to the biology of gene effects.

The substantive findings are too numerous to discuss but attention should be drawn to two. First, it is often supposed that genetic influences are stronger in simple organisms, but the evidence does not support this supposition. The heritability of anxious behaviour, for example, is much the same in humans and in mice. Second, genes are usually pleiotropic – being versatile and participating in many different processes. Non-geneticists frequently scoff at studies of fruit flies – how could these possibly be informative on the behaviour of humans? Of course, it is crucial to be careful in the level at which parallels are drawn. Nevertheless, animal model systems investigating the genetics of circadian rhythms and of geotaxis (i.e. the organism's tendency to go up or down) are clear-cut in showing that there are not specific genes for either. Rather, the resultant behaviour is influenced by genes whose main effect is on something else. The clear implication has to be that the search for genes ‘for’ schizophrenia or autism or depression will not succeed. It will be possible to identify the biological causal pathways involved but that goal remains some way off.

Altogether, this is a very good book that all psychiatric geneticists, and all psychiatrists interested in biology, must read (and preferably own, so that they can easily refer to it), as well of course as the general public. The review has been lengthy just because of the book's excellence. Minor suggestions have been made for possible additions to its coverage, but that already provided exceeds anything in any other comparable book.

A must read!