I just had a look at the book to give some examples of actual species numbers versus the number of species featured in the book.
Some groups come out really well, which might reflect the artist's interests (?) - for the callitrichids, six out of six Callithrix, ten out of fourteen Mico, sixteen out of seventeen Saguinus.
But then you've got examples like only four out of twelve Cebus, three out of seven Tarsius, three out of seventeen Microcebus, three out of twenty Galago, seven out of twenty-four Lepilemur, five out of twenty-nine Callicebus, etc.
Oddly, there are five inclusions for only two species of Varecia (i.e. the book includes three subspecies of V. variegata plus hybrid V. variegata X V. rubra). Both subspecies of Indri are considered desirable enough for inclusion.
It is a book of beautiful illustrations, but not quite what I was expecting. I wouldn't say I was disappointed, as such, but not entirely happy. I had been very surprised by how slim it was when I opened the package - I had been expecting a weighty encyclopaedic tome.