There's not a huge amount of books about the the Irish passage graves ,so a new one is welcome . I enjoyed it , it's main concern is the evolution of the monuments and as such a typology is intoduced . Type 1 is the earlier monuments with small with the chambers usually surrounded by a circle of boulders with little space between them discouraging access . They have a rudimentary passage no covering cairn , art , associated astronomy and were too smll to allow for access for rituals and if there were any it would have to have been outside the monument .e.g. much of the Carrowmore complex . Type 2 allowed access and repeated entry into the chamber , they have art , astro associations , are much bigger than earlier , corbelled roofs , in relatively more isolated situations , more recesses and are also the most common of the monument type (75%) e.g. Seefin ,Knockmany , Belmore etc . Type 3 were even bigger , had straightened facades, platforms ,greater association with quartz ,stone settings , kerbstone art ,associated linear monumnets and prestige artefacts e.g. Knowth ,Knockroe , Newgrange etc.
The weakest part of the book for me is suggestion of a connection between the types and the two modes of religiosity and ritual proposed by Harvey Whitehouse i.e. Imagistic and Doctrinal with type 1 being associated with the former and type 2 and 3 with the latter the binary distinction is too neat and there is no mention that Whithouse accepts that both can be be found to co-exist in the same cosmology/culture.
As the author does know the subject , it is informed guesswork and he is never dogmatic when there is doubt .