The majority of the book approaches the science of brewing from grain to water to hops to yeast and then into the brewing process itself. It dives deep into several subjects without melting your brain with too much technical discourse (for those of us who are not scientifically-minded). There are small bits of information that I had read/heard about before but without as much substance as I found here.
The heart of this book is really around the mash process. New Brewing Lager Beer spends a considerable amount of time explaining what does on during the mash and particularly how to perform different mash schedules with most of the attention given to decoction schedules. He explains the science and reason for each rest period and makes it very obvious that the mash is probably more important and deserves a lot more attention than most homebrewers tend to give it. One point Noonan makes without drawing sufficient attention to it is that the decoction mash is intended for undermodified malts rather than the well-modified malts used by most brewers today. Some of the debate over decoction mashes that takes place today tends not to factor in that very salient point.
The book turns discussing the fermentation schedule and that's where it hits the information about preparing yeast for lager brewing, the fermentation schedule and of course, lagering. I was actually surprised by how little of the book this section filled. I'm not sure if Noonan just thinks there's very little specific requirements on the back end of fermentation or got tired of writing in such detail by this point (I'm sure it's the earlier explanation). However there is still plenty of information and enough to understand what needs to occur before lagering kicks in. The book offers a few simple recipes for traditional German lagers as well.
Overall the book does a good job of approaching many brewing subjects to prepare you to brew lagers while most homebrewing texts purposefully or inadvertently focus on the ale process. Even if you have very little interest in brewing lagers it's a good read on the science of brewing and you can gleam lots of small details about improving your mash and kettle processes to make better ales. I think it's a good read after the usual texts (and even Gordon Strong's book) and maybe before reading the new, more technical books like Yeast. One thing to keep in mind is that the book was originally written in the 90s and last updated in 2002. There are some points made that have been debunked (fully or partially) since then but I think most of that has to do with improvements in the quality of ingredients and equipment available to homebrewers.