I definitely recommend this site! It has everything you need to find a name for your character(even a random name generator). It is the only name website that I use when I need some naming inspiration!
Looking for unique baby names? These rare boy names were given to just 8 boys in If you love cool boy names that no one else is using, this list is for you! (Most of these I wouldn't use or recommend, but there are some pretty cool names on here)
Ok, so it's not a "book", but I TOTALLY prefer this site to the Baby Names books that you actually DO find on the market. I love the HISTORY it provides for the name, more than just Elizabeth - Hebrew - "My God is my vow.