How to Judge if an Academic Book is Useful or Not
(Or at least that's how I learned to do it at the History department of my North American university in the late 2000s - early 2010s. Some details may vary.)
A title is obviously not enough, but don't worry, I've been fooled myself by titles that seemed really good, and then the contents didn't really match. Don't blame the authors, they have little control over that. The publishers wanted to market it and make more money from books that are kind of niche.
The short summaries in the back? Well they're not very detailed... Sometimes they're just praise from other historians. Not the most helpful.
What you really need to check is the table of contents. It's a much better indicator than a title or back summary. Some are very detailed too!
History books often have forewords. They're written by a senior historian, someone who supervised the thesis this book was based on, etc. Sometimes it will have more than one foreword, especially if it's a classic that's started to age. This is where you find information about the author. This is where you'll find out if the author is a historian or someone of another trade who picked it up as a hobby or is doing a serious second career out of it, if there are flaws or biases in their research, if they have an agenda they are willing to admit to or not. Because subjectivity is not BAD. Pure objectivity is a myth. You teach that to first year students because it's easier and otherwise it might make teaching (and grading) a nightmare. First you need to learn the basics. Then you learn how to interpret. Only after that can you pick your side. (I mean, you can pick it fairly early, but you have to be aware that there are sides, because there are always sides. You just have to know what it means to choose that side because yes they are political choices too.) The foreword is also usually where you will learn if this book resulted or was part of a controversy. Causing or being part of a controversy doesn't mean the book is bad. Some topics are just... like that. The French Revolution, for example, is like that.
A note: if it's a book with multiple authors, there will usually be a shorter section that gives you a summary of what each author has published most recently, works on, where they studied, etc. You most likely have a specific type of academic book in your hands: the printed result of a day or two of conferences historians held somewhere in the previous year.
Next you look at the introduction and the conclusion. The introduction might also mention if there's a controversy, in which case the book inserts itself into a longer tradition of it, and isn't sparking anything new - it's already existing. The introduction might also have the author give details on themselves. Usually there should be a section that introduces you to what each chapter/part of the book is about. That's how we learn to write introductions. But it's tedious to do, so not everyone sticks to the formula. Introductions sometimes are... just not that. It's up to the author, and how traumatized they've been by academia I guess.
The conclusion should recap, obviously, but it also showcases ways this book can help bridge the gap between preexisting research that's lacking in some way and future research that could fix that. It's also where the author might connect the past to the present, and talk about how history is relevant to the present day. Well, that's how I write conclusions anyway. There's a bit more leeway, depending.
Bibliographies are you friends. Study them. Look at the titles. Look at authors mentioned. Repeat the process.
One last note: if a book doesn't have footnotes, don't necessarily consider it garbage. There are publishing houses that refuse to do footnotes, even end of chapters or end of book notes. There are authors forced to sacrifice their notes in order to be published to a prestigious house in a sort of Faustian deal. Sacrificing your notes mean sacrificing the entire critical support system of your study. That's where your research happens. Sometimes my footnotes take two-thirds of a page. It's not fun to read (I don't know, I think it's fun), but that's how research is. But the Great Public doesn't seem to Like That. Or that's what publishers believe. There's a lot of socio-politics involved in publishing, and it's not very fair - unsurprisingly. You might have to go back to look if the book was based on a thesis. Bernard Vinot's biography on Saint-Just (396 pages), which is one of the best that exists, has no footnotes, but it was based on his PhD thesis which makes up three volumes and almost a thousand pages if I remember correctly. That's not a format publishing houses like very much alas. There's enormous work involved in turning your thesis into a book that can be published... and no guarantee it will be published. Again, socio-politics.
