This book should be part of any collection for those interested in the recent (c 1980) revival of interest in the runes. It is still the highest selling rune book internationally, but also one of the least researched.
When it was first published, the academic sources were not very available to the public, although they would have been available to Blum had he made the effort. Instead, he created a simple divination system, based more on his own readings of the I Ching than the known historical sources of runic knowledge.
There is a wealth of information in the old rune poems, and in the original futhark ordering of the runes. Blum ignores both. However, at least Blum never claimed to be reconstructing an old system. On the other hand, unfortunately, most of his readers assume that there is some real historical content in the book.
For those who are looking for an esoteric book about runes based on, and respectful of, our real available historical cultural heritage, this is certainly not it.
I would recommend Pollington's "Rudiments of Runelore" to provide a minimum factual background, before wasting time on any of the New-Age manuals.