Having a field guide makes a huge difference to travelling on safari. Many of the following are not published in the US, but are easily found in Kenya itself.
Mohamed Amin, Duncan Willets and Brian Tetley The Beautiful Animals of Kenya (Text Book Centre, Kenya). Lavish photos but sparing text, an easy, lightweight book, but more a tourist souvenir than a serious guide to Kenyan wildlife.
Michael Blundell Wild Flowers of East Africa (o/p). Botanical companion in the series.
Jean Dorst and Pierre Dandelot Larger Mammals of Africa (HarperCollins, UK). Readable and accessible with lively illustrations, though it tends to favour classifying many races as separate species.
Richard E. Estes The Safari Companion (Chelsea Green, UK) This book aims to explain not only what animals you're looking at, but also what they're doing, and its illustrated explanations make fascinating reading.
T. Haltenorth and H. Diller Mammals of Africa (HarperCollins, UK). A rival for Dorst and Dandelot, which tends to find fewer species in the variety of mammals out there. With its superabundance of detail, this might look like first choice, but the somewhat stylized paintings are less meaningful than Dorst and Dandelot's when you're thumping through the bush, and much of the text is superfluous for all but the professional zoologist.
John Karmali The Beautiful Birds of Kenya (Text Book Centre, Kenya). Like its companion volume, Beautiful Animals , a tourist souvenir of Kenyan birds with lots of colour photos.
Jonathan Kingdon The Kingdon Field Guide to African Mammals (Natural World, UK) A detailed and comprehensive catalogue of African land mammals, illustrated with photographs and distribution maps for each species.
Ray Moore Where to Watch Birds in Kenya (Transafrica Press, Kenya). Invaluable tips and background for the devoted bird-watcher.
Ber van Perlo Birds of Eastern Africa (HarperCollins, UK). An essential pocket guide, providing clear colour illustrations and distribution maps for every species known to occur in East Africa, though little by way of descriptive text.
Dave Richards Photographic Guide to the Birds of East Africa (New Holland, UK). Over three hundred colour photos.
Chris Stuart and Tilde Stuart Field Guide to the Larger Mammals of Africa (New Holland, UK/Ralph Curtis, US). Good field guide published in the late 1990s.
Nigel Wheatley Where to Watch Birds in Africa (Christopher Helm, UK/Princeton University Press, US). Tight structure and plenty of useful detail make this a must-have for serious bird-watchers in Africa; 25 pages on Kenya.
John Williams Birds of East Africa ; Field Guide to the Butterflies of Africa ; National Parks of East Africa (all HarperCollins, UK). Birds is the standard spotter's tome. Butterflies is exotic and useful - if you can get hold of a copy. National Parks covers parks, reserves, mammals and birds, but there's too much space devoted to long lists of fauna, and the practical details for the parks are too dated to be of any use.
Zimmerman, Turner and Pearson A Field Guide to the Birds of Kenya and
