The only book I have readily to hand on Lettow-Vorbeck is 'The Great War in Africa' by Byron Farwell (pub. 1987 by Viking). One of the few books on WW1 and Africa. Possibly re-published in paperback more recently.

I am sure there was an article on the failed British landing on the then German East Africa coast, in the Western Front Magazine recently. Cannot readily put my hand on that. The role of the commerce raider Konigsberg features irregularly in the WFA magazine.

Hope that helps.