I would put it in the same category as most of the other major reloading manuals. It has a lot of good how-to information on the fundamentals of reloading techniques, safety stuff, do's and don'ts etc. It also has a lot of load data for specific cartridges that you will not find in manuals geared towards that particular company's products. As an example, you will find non-Hornady component combinations in the Lee manual, whereas the Hornady manual only lists Hornady bullets.
The previous statement is meant as an example only. I do not intend to go dig out my Hornady manual to verify this. I am illustrating the concept. Lee makes reloading TOOLS and equipment, not bullets, brass etc. They do make bullet molds but that is as far as they go TO MY CURRENT KNOWLEDGE.
In that context, IMHO the Lee Manual is a worthwhile addition to any reloader's library. And I have used many of their products like the Factory crimping dies, bullet molds, etc. Even have a Pro 1000 set up as a dedicated 9mm progressive loader. As it is a three station press, I only use it case mouth flaring, powder charging, bullet seating/crimping. Works a charm for me. I have a dedicated universal depriming press, and do all my case prep off press. For 9mm blaster and target ammo it works great.
Get the manual.