Aule, I have Robert Fosters Guide and find it wonderful. I haven't seen the one you have, though.
As to more Tolkien books, I love Tolkien: Author of the Century by Tom Shippey. It analyzes LotR, the Hobbit, The Sil., Leaf by Niggle and Farmer Giles of Ham. It also points out some ancient literature from which Tolkien may have drawn his ideas.
If you are interested in books about Tolkien as a person, I strongly recommend Humphrey Carpenters biography, called simply Tolkien, and The Letters of JRR Tolkien, also compiled by Carpenter.