Among the approximately 3,000 references to Solar deities in Hittite texts, 100 belong to Old Hittite (= OH) and 400 to Middle Hittite (= MH) sources (p. 8). Steitler arranges his study using a strictly chronological approach: OH (chs 4–6) and MH (chs 8–10) sources on the Sun goddess (of Arinna), the male Sun god and the Sun goddess of the earth, also taking into account local solar deities (ch. 7) and concluding with a section on kingship and solar deities (ch. 11). He thus substantially increases our knowledge compared to earlier studies by Daisuke Yoshida and Ulrike Lorenz-Link.

One strength of the book is the precise description of different solar deities according to their historical development, resulting from the re-arrangement and new edition of a number of texts (CTH 339.1; 339.2; 339.3; 634.3; 736; 764.1; 820.4; 820.5) and also including some new philological insights. The following are worthy of mention: the element -šemu of the Hattian divine name Wurunšemu (pp. 59–64) is neither related to a word for “mother” nor to Hittite “šepa” (“genius”), but the goddess's name must be analysed as “the earth (wur = un), its (še-) mu” with unknown semantics of mu. The Hittite word šiu- (and šiw(a)- in Old Assyrian names as well as other related lexemes) only means “god” in general and not “Sun god”, thus ruling out the interpretation of “Šiu” in the Anitta text as “Sun god” (pp. 184–90). The title “My Sun” (and variants) as an epithet of the Hittite king shows with different phonetic complements (pp. 436–44): ^dUTU-mi/e- “my Sun” is only used by the king himself in the 1st person or when somebody addresses the king directly in the 2nd person. ^dUTU-šummi/a- “our Sun” is only mentioned in contexts referring to the king in the 3rd person, while the last phonetic complement ^dUTU^ŠI-i- can be used in all three cases. All these precise philological observations contribute to a better understanding of many texts.

Regarding the position of Solar deities in the history of religions in Anatolia, the first result is the proof of the important position of Eštan (Ištanu) as female solar deity in the Hattian milieu. Sequences of divine names in festival texts (pp. 47 sqq.) mention Ištanu (or Ištanu-Tappinu) in the primary function, followed by the Storm god. For the ideology of kingship, the female Sun goddess, the Storm god, and Inar are the main gods who legitimize the king (pp. 167 sqq.) – from the OH period onwards. While it is beyond doubt that both a Palaean and Luwian Sun god are attested during the OH period (in Palaean of a more minor rank than the storm god Zaparwa, pp. 221–3; in Luwian as head of the pantheon, pp. 202sq.), there is no evidence for a Hattian (or Old Hittite) male solar deity. When a Sun god (occasionally) occurs in the Old Hittite period, he is neither a Hattian nor a Hittite but a Luwian deity. The third solar deity in OH sources is the Sun goddess of the earth, who is best attested during the early period in the prayer CTH 371 which belongs to the Luwian milieu. In conclusion, next to some local cults (pp. 247 sqq.) we find the following solar deities in the OH period: in the “Hittite state pantheon” the main position is held by the (Hattian) Sun goddess Eštan as wife of the Storm god. A male solar deity – in different positions – is known only among the Palaean and Luwian milieu from whence both Sun gods are introduced to the Hittite state cult, but not as focal points for early Hittite kingship as the king's authority depends on his relation to the Sun goddess and the Storm god only.

This OH situation radically changes in the MH sources when the former marginal male Sun god reaches his new status (pp. 329 sqq.), prominent now in festival texts and magical rituals. The most significant change and “exaltation” of the Sun god can be seen in prayers (CTH 3723–374) which are “very close adaptations or mere translations of Mesopotamian literature within the genre of Hittite prayer” (p. 371). In this way since MH times the Sun god can be seen as the righteous judge with his pre-eminence both in the pantheon and the entire cosmos. Despite the fact that these prayers ultimately go back to Mesopotamian traditions, he is no longer a Mesopotamian, but the Hittite god. Contrary to the Hittite Sun god, the Hurrian Sun god Šimige does not gain an important position in the Hittite state (pp. 407 sq.) despite his spouse Aya(-Ekalte) occasionally being identified with the Sun goddess of Arinna (pp. 310–2). The Sun goddess of Arinna continues the “Hattian” Sun goddess from OH times, changing only the name but not the functions of the Hattian goddess. In Arinna local festivals (CTH 634; 666) are celebrated for her, and together with the Storm god she is the main goddess in the festivals of the state cult. Contrary to the Sun goddess of the earth (pp. 419 sqq.), there are only very limited references to her in magical rituals (p. 281). The last section of the book discusses the connection between solar deities and Hittite kingship. This topic is mentioned mainly in juridical and administrative texts and magical-juridical rituals but rarely in festival texts where the close connection of the king with the Sun goddess continues. Steitler also discusses aspects of the royal iconographic tradition (pp. 444 sqq. compare to this topic most recently M. Hutter and S. Hutter-Braunsar, “König und Gott. Die ikonographische Repräsentation der hethitischen Könige”, in J. Gießauf (ed.), Zwischen Karawane und Orientexpress, Münster: Ugarit-Verlag, 2017, 155–74). A very short outlook on solar deities in the Empire period refers to the necessity of further research into the ongoing chronological development of the Solar deities, concluding this ground-breaking study of aspects of Hittite religion.