Highly recommend for world building, every word is a jumping off point.

This book is a lot of fun for me. A lot of terms that I wasn't familiar with, some that I was. This is a pretty good help for writers or if you just want to study into the medieval period a little more.

One drawback is that it's not really set up like a dictionary, but more like a book; less easy to navigate around to keep coming back for reference.