Initially, I used Google: Book Blogs Search Engine.
If you want to find bloggers for the Mystery section, then write the word Mystery into the search engine. Numerous addresses will pop up. You can copy the addresses to Excel. Why? Because some addresses will keep coming up. If you copy them to Excel one below the other, you can then sort the column in alphabetical order and delete the addresses that appear more than once.
This way I found around 400 book reviewers for crime novels. And how many agreed to read my book? Only 30.
You must realize that most bloggers are very busy, so you must be patient.