Others say...

"excellent source for beginner documentary makers"
Before you pay a lot of money for a documentary filmmaking class, I strongly recommend this book. It seems to cover all the bases of the process (don't expect much info on equipment though) and includes insightful anecdotes from real situations. Rosenthal guides you through the entire evolution of a documentary from the conception of the idea, writing proposals, dealing with sponsors, locations and crews to distribution to the ethical responsibilities of a director. One distinguishing factor of this particular book in comparison to other books on filmmaking is its spectrum-from independents to corporate to public service films.

"A fairly comprehensive guide"
Rosenthal has written a fairly comprehensive guide for aspiring and new documentarians. He covers everything from initial idea through proposal to marketing and distribution, including delicate topics like how to explore your initial idea and figure out if it's any good, and where to look for funding. He mentions a lot of details that are easily missed by amateurs, all of which could be disastrous to production. My only reason for holding back a star is that I would have liked a bit more depth to the examples (e.g., a full sample budget instead of an outline of what to include).