In recent years, studies on populist radical right parties (PRRPs) have been numerous given their electoral success in recent years. This literature has focused on explaining both the supply and the demand side that is, by analysing micro and macro explanations of the phenomenon. However, a study focused on populist radical right parties' alliances in the European Parliament (EP) has been neglected so far, even tough this party family in Europe first achieved success in the European elections and then at the national level. McDonnell and Werner's book is the first attempt to do so.

The book tries to explain how PRRPs in the EP build alliances. In this sense, the main question they want to address is: Why do PRRPs join specific groups in the EP? For doing so, and adopting the ideational approach, they examine nine PRRPs: Danish People's Party (DF); Finns Party (PS); UKIP from the United Kingdom; Sweden Democrats (SD); the French National Front (FN); the Italian Northern League (LN); Austrian Freedom Party (FPÖ); the Dutch Party for Freedom (PVV), and the Belgic Flemish Interest (VB).

The three main hypotheses that the authors formulate to understand party coalition agreements are (1) party congruence (they analyse EU integration, anti-immigration, and left-right positions of the main political parties in the coalitions thanks to the Chapel Hill expert surveys); (2) office-seeking arguments, for example, economic benefits (higher founding for each party) and more visibility due to their participation on the coalition group (they found this information on the European Parliament's webpage); and (3) alternative explanations like national interests, conflicting types of nationalism, tensions between nationalities and fears about being tainted by association with one another (p. 31) were tested through semi-structured interviews with relevant MPs of the analysed political parties.

Thus, chapters 3, 4, and 5 are focused, respectively, to understand why PS and DF opted to join UK Conservative in the European Conservatives and Reformists (ECR) group instead of joining the closest group like Europe of Nations and Freedom (ENF); why UKIP and SD build a coalition [the Europe of Freedom and Direct Democracy (EFDD)] with the populist and also Eurosceptic Italian 5 Star Movement (M5S) instead, be part of ENF and, finally, the movements that different PRRPs did to build the ENF, without doubts the most congruent European populist radical right group (it is integrated by FN, FPÖ, VB, PVV, and LN).

McDonnell and Werner's analysis clearly underlines that, among other explanations, reputational ones are the main drivers of DF and PS movement to join UK Conservative in the same group (in terms of party congruence the three parties are very distant, both regarding positions of the EU integration process and attitudes towards immigrants). Thus, DF and PS want to distance themselves from the UKIP, and that is the reason why they opted to leave their EP group in 2009. Furthermore, being involved in the same party coalition than the UK Conservatives gives both parties legitimacy to be perceived as potential coalition partners at the national level. The interviews reveal, as well, that being involved in the ENF (a much more congruent option) could be negatively perceived for the electors at the national level, as join parties like the FN and FPÖ with a fascist past could be something like ‘shoot himself in the foot’. In this sense, Chapter 4 also underlines that UKIP does not join ENF because of reputational costs on the national level. Additionally, and more importantly, UKIP opts for being ‘alone’ in the EFDD, despite the incongruence with M5S on immigration and more generally on ideological grounds, because of better economic conditions and higher time of intervention in the EP. With regard to M5S and SD decision to join EFDD, it seems clear that the M5S opted for the ‘pre-nuptial’ agreement with UKIP and joined the same party group because of their independence inside the group, while SD rejects the option to be linked with parties such as FN, and, as a consequence, EFDD ends up being its only option. Finally, ENF is clearly the coalition group with the higher party congruence: the same ideology, the same stance on both immigration and anti-European integration positions. The members of the ENF were aware that the European alliances might prompt negative responses from national media. But rather than avoiding the risk, they tried to break the vicious cycle of reciprocal demonization (p. 159).

The book clearly reveals that against the dominant theory, the one that poses the relevance of party congruence in order to understand coalition agreements, the semi-structured interviews revealed that reputational costs were the main factors to understand the coalition of PRRPs on the last EP. Thus, this book is not just a good understanding of PRRPs movements at the European level, but also a fantastic tool to understand recent rare ‘populist’ agreements in different countries: like the M5S and Lega coalition at the beginning of the Italian legislature. Additionally, the book reveals that the coalition with a high level of congruence, ENF, does not vote together, exhibiting low levels of party voting discipline. In sum, a PRRP great European coalition, like the one of People's Party of Socialists and Democrats, seems difficult to imagine in the short term. And, although they dream with a ‘global movement’ differences and particularities of the different parties, act as a barrier for a real transnational populist agreement.

McDonnell and Werner's contribution clearly means an improvement in the understanding of PRRPs coalition agreements, underlining the relevance of reputational costs for the political parties, rather than their policy congruence. In this sense, the book emphasizes that ENF could mean the first step to a further consolidated PRR European group although, currently, more time is needed to really mean a well-cohered force. In this sense, on theoretical and empirical terms, this book is an insightful piece to understand the future development of this political family in Europe and abroad.

However, by reading the book, many issues arise:

• First, since interviews with the MPs reveal the reasons to join one or another European party group, I would expect a much more detailed analysis such as systematic and quantitative analysis of their content could be a considerable improvement for the book. In fact, interviews are the most original and innovative contribution of this book and the fundamental piece to understand party coalitions at the European level among PRRPs.

• Second, I believe that given the agreements after the 2019 EP elections, Identity and Democracy (ID) substitutes ENF as a ‘congruent’ PRRFootnote ¹ and it would be really interesting to know the reasons behind these the agreements with the different political forces: why did the PS and DF decide to join the same group that FN and FPÖ, was it because of Brexit or because of the commitment to configure a global populist movement? On the other hand, why the M5S (with 14 MPs) decided to join the Independents? This is likely to change after the national agreement with the Partito Democratico (PD)?

• Third, it could be the European Conservatives and Reformist (ECR), the group that includes political formations like the Spanish Vox, the Polish PiS, the Italian Brothers of Italy (FdI), the Dutch Forum for Democracy (FvD), and the Greek Solution (EL) be defined as a Eurosceptic far-right coalition? To what extent ID can be depicted as a Eurosceptic radical-right group whereas ECR is an extreme (soft-Eurosceptic) party-coalition? We are waiting for the second part of the International Populism by McDonnell and Werner to deal with all of these relevant questions.