Can I include an extract of another persons book in my blog with references?
If so, are there any restrictions that I must follow?
This depends a lot on the context and scope. If you simply post excerpts from a copyrighted work without any commentary, criticism, or analysis, you're pushing your luck (even if you include attribution). If, on the other hand, you need to include some excerpts as a part of an article of your own that, for instance, analyzes the work in question (or compares it to others), this is generally acceptable, within reason (= you can post a paragraph or two, but not any extensive blocks of text).
Yes, you can, so long as it meets the criteria for "fair use." For more background, I recommend reading the following Wikipedia topic: https://en.wikipedia.org/wiki/Fair_use