First let me say that I have spent the last several years reading close to 3,000 books in a sort of spiritual journey/quest for "enlightenment" (whatever that means, and assuming there is is such a thing.) I've read just about all the great "classic" works--everything by Plato and Jesus, tons by Buddha, along with mega-amounts of ancient and modern philosophers and thinkers, both Eastern and Western, etc. that I could get my hands on. Yet this book has managed to astound me. It's close to 800 pages, and huge. Unless you go on a non-stop reading binge for a couple days, you'll take weeks to read this entire thing. Which is just fine, because on almost *every* page there is a quote that either (a) helps me see something from a perspective I haven't quite encountered before, or (b) expresses a thought i've already encountered, but expresses it in a way that is so pithy and fresh and memorable that I want to run out and share it with the people I know (and in some cases I've done just that!). And then you will want to read it again. And again. And again . . .
The book is very well organized. Each chapter covers from between 1 to 7 pages or so of a different topic--e.g. "compassion"-- with quotes arranged in roughly chronological order of the year of the person being quoted. The headings to each chapter have extensive cross-references so that the reader can look up related entries, either similar concepts or opposite concepts. An extensive bibliography at the back lists all the entries in which each author appears. One minor gripe I have is that the source of the quotes is not as well documented as it could have been. Some of the quotes have specific works listed, but many do not, so that (a) the reader is left merely to trust that the compiler is correct in quoting from that speaker, and (b) the reader has no way to read further in the work quoted. Still, wisdom is wisdom, and even if there is no way to verify who said what, an anonymous truth found on a crumpled up piece of paper on the street is still truth!
Also, the reader might think of a topic or two that should have been given a separate entry but wasn't (e.g. there is no entry for "beauty" which in my mind is essential for a book on "spiritual wisdom.") But still the entries are fairly exhaustive in their coverage overall.
One other minor gripe is that the author focuses much more on modern (1800s and especially 1900's) thinkers than on ancient wisdom. People like Plato, Aristotle, Jesus, or Buddha for example (all of whom I'm quite familiar with their work), could have, and should have been, quoted much more extensively than they were, especially when numerous modern, very recent authors were given far more quotes than any of them. Still, as I said above, truth is truth, regardless who says that truth.
This is a reference book that you will keep not just on your shelf, but on your coffeetable or nightstand, for easy access, and perhaps permanently. And you will enthusiastically recommend it to everyone you know. And you will loan it out. And you will buy it as a gift for people. In fact, if I the money, I'd buy a copy and give one to all my family and friends--but alas, I don't have such money. Probably because the book is so huge in volume, a cloth (hard) binding is very helpful to keep the book's integrity intact. Nevertheless, I hope this book is released in a less expensive paperback form soon. Either way, though, this book is well worth the price (and probably more). You will *not* regret buying this!