There's no manual for Lightroom. The help files are “crappy” shall we say. That's why, there are people like Scott Kelby “raking the dough.” But at 450 pages, that's a lot, for many people it's overwhelming and very detailed. I bought it and even today, I still use it on a weekly basis.
Adobe wrote a very nice, free and easy to comprehend gettting started manual, 75 pages, in PDF format, available at: