Please correct me if I am wrong on this one but as far as I am informed, detailed maps of Kenya were always hard to come by since that infamous AirForce coup in 1982 in Nairobi, Kenya, upon which the Government of Kenya reduced the number of detailed maps openly available to the public.
A friend of mine had told me about some plots for sale in Thika (Kenya), so I did a short Google image search on the keyword "Thika" and came across a HUGE collection of amazingly detailed maps for scientific use – scanned & published online by the DG Joint Research Centre of the European Commission: the "European Digital Archive on Soil Maps of the World (EuDASM) ".
Kenya? Africa? – you name it, they have it. Free of charge! With coordinates for geo-referencing and other useful metadata!
Now I take it that most of you won’t have a proper use for such scientific maps and that Isohyets of median annual rainfall for places like Wajir won’t be of any interest, BUT! I know you’ll love to have a look at maps like this one showing the City of Nairobi:
Or this 1:100.000 map of "Nairobi & Environs":
As for the soil question in the area around Thika, Kenya:
Those maps for Kenya make up for about 1 GB of downloadable JPEG images with an average size of 4 MB each…ENJOY! :-))