Not my area, but here is a good general rule of thumb: Look at the works cited by the books in the book list. All the books in the book list should be well done scholarly works that engage with the surrounding literature on the relevant subject. For instance, I recommended Descartes: An Intellectual Biography in the history of philosophy book list, which contains 5 full pages of sources cited in the text. So if you want to know more about a specific period, check out the works cited / bibliography of one of the books you've already read.