Finding field guides to plants, animals and birds whilst in Namibia is relatively easy; though it can be difficult outside of the country.
There are some comprehensive little hardback guides on the flora of various areas, including Namib Flora
and Damaraland Flora
published by Gamsberg Macmillan in Windhoek. These are sold in Namibia and marketed with visitors in mind as well as locals.
The standard birding guide to travel with is still Newman's Birds of Southern Africa
, which is widely available overseas. For mammals, Chris and Tilde Stuart's Field Guide to Mammals of Southern Africa
is generally very good.
The Shell guides to The Namib
are excellent for appreciating the area's flora and fauna. Doubtless more will appear for various other areas in due course.