I had the same concerns about only one keyword and not learning the pronunciations, but I found his book was the only method that worked. Everything else I tried, I would give up after 100 kanji or so, cause it got too confusing. With time, assuming you are also using other material for your studies, the pronunciations and other meanings just start falling into place. And eventually you start forgetting the silly stories, and just learn the meanings- but the stories help get you there. When I see 空 now, to be honest, I forget if the Heisig keyword was "empty" or "sky", but the keyword sure helped me at the time.
I wouldn't bother with books 2 or 3... Book 2 covers pronunciations, but doesn't do anything special to help you remember them. Book 3 goes takes you up to 3,000 kanji, but after learning 2,000, I think it's easier to just look up anything you don't know in a kanji dictionary.
P.S.- The link I previously listed for the first 250 pages of the book came from
www.kanjiclinic.com, which Heisig is familiar with (he previously posted an answer to a question I had submitted to the site), so I assume it's a legal copy.