Recommendation: medium/low, basic level finds
The Mysterious Bible Codes was first published in late 1998 and in paperback in 1999. The findings are more basic than the current level of research in the codes with phrases and sentences. Grant Jeffrey was prone to claim more at the time than his findings warranted as far as statistical significance, although he has some interesting Hebrew matrixes from the Torah and from Isaiah 53. His claims in the book of valid codes in the Greek New Testament are absurd. He finds a couple of words and claims this proves a code in the Greek NT. What he found in the Greek NT, in citing a couple of words, is nothing more than what might expect randomly in any text. I'm not saying that there is or isn't a code in New Testament, what I'm saying is that Grant hasn't made even an interesting case for the possibility of it with his finds.
I think you'd find this book interesting from a historical perspective, in seeing how some people can claim more than is warranted by their findings. As I said, his Hebrew matrixes are OK, although he doesn't show them in matrixes. He shows them as lists of finds. I think any book on the codes should show the matrix displaying the terms. The reason is that you as a viewer want to see how close topically related terms are together. If they aren't close, then the matrix tends to mean less to me.
Mysterious Codes is available at Amazon.com and Barnes&Noble.com. in paperback; and at Barnes& Noble.com, I saw that they have the hardcover version available at 80% off and less than half the price of the paperback version. So check around for a heavily discounted version of this book.