This is one of those times where sharing your location in your profile helps others to help you;)
In my case, I am looking at cool temperate climates, and
Eric Toensmeier has helpful information, both on his own and in the two volume food forest work he did with Dave Jacke. Martin Crawford has a food forest book with very helpful information, and nicely arranged. I have found that, so far, crawfrod's work has had the most accessible format, with information well organized and cross referenced, such that it is easy to see which nitrogen fixers are good for chop and drop, or make good forage, or both.
If I were going to make a somewhat blind suggestion, it would be Martin Crawford's book.