I think this is one the best books on African weapons without venturing into more publications on regional art that include weaponry. Manfred A. Zirngibl & Alexander Kubetz. Panga Na Visu.
https://www.amazon.com/s/ref=nb_sb_n...=panga+na+visu
I am very keen on African weapons. I used to collect them and still have a few. There are fakes but with a bit of experience they are rather obvious. I think it still possible to get very good pieces at reasonable prices but very nice pieces especially Congo and throwing knives can command high prices, but pace yourself as although costly some weapon forms can be extremely common and you may not get much in the way of resale.