Try JSTOR. You can get a free account, and pretty much any prominent pop-history or really any pop-academia book will have reviews on that. JSTOR is mainly a source for digitised academic journal articles, which is where most scholarly reviews will be published, so just run the name of the author and the book through the search and you'll find plenty of hits. It does depend on the book, since it may or may not be important enough to even have reviews.

Edit: Also, try Google Scholar. A lot of the links will take you to JSTOR pages, but using different search algorithms may help you to pick up on specific articles that you may have missed or are more relevant.

For ancient history, check out Bryn Mawr Classical Review. Other disciplines may have similar.

To add to followup questions, as a history student, I often use J-store to find reviews from historic magazines with specialised content, for example the "William and Mary" is great for reviewing 18th century England. A review from there on J-store is likely written by someone intimately familiar with the material. After some four/five reviews, I check if there is a pattern emerging and base my reading strategy of the book or article on that. If a review jumps out of the crowd, I look at the author of the review, what is his specialisation.

Lastly an important thing to note which my professor taught me. The academic world has a lot of competition, especially within fields. Because reviewers disagree with the book, does not mean the book is definitely bad. If they disagree in source interpretation, but state the research is good, it is just academic debate. So check how they disagree and on what, and thus, while reading disputed sections, be aware others disagree, but don't immediately discount something because one person disagreed.

There used to be a subreddit, /r/HistoryResources, started by one of the moderators here, /u/Daeres, dedicated to reviewing history texts, but it died a few years ago. I think the only active moderator there who is still active in this sub is /u/Tiako.

Edit: I do not post this in the belief that it will be helpful to you, but in the hopes that it becomes active again.