When the 10-volume Routledge Encyclopedia of Philosophy (REP) was published in 1998, it was widely acclaimed as the superlative philosophy reference book of its time, ending the unchallenged 30-year domination of Paul Edwards's MacMillan Encyclopedia. However, even though the REP was also made available online, it has always been priced out of the reach of individuals. For those without institutional access to the REP, the next best thing was the single volume concise version. Essentially comprising all the introductions to the longer entries of the full edition, the Concise never really worked. It had entries on more subjects than you knew existed, but failed to tell you enough about the ones that really mattered. It was like a greatest hits compilation made up of one-minute extracts from every song the artist recorded. It was a poor advert for editor Edward Craig's mammoth achievement and could not be considered a credible alternative to Ted Honderich's rival Oxford Companion to Philosophy.

Now Routledge have had a second stab at extracting a single volume from the REP. The result, The Shorter Routledge Encyclopedia of Philosophy, is a vast improvement, which seems to have been compiled with more attention to what potential buyers would actually want. So out go many of the more obscure entries and more space is given to key concepts, areas and thinkers. That's not to say the breadth of the original has been entirely removed. Daoist philosophy remains, it's just that it is no longer preceded by Dai Zhen, Damascus, Peter Damian, The Aesthetics of Dance, Dao and Daodejing.

Also chopped are the further reading suggestions for the shorter entries. If there has to be a quid pro quo, then trading these for more actual information in the book seems the right choice. But it is a pity to see them go, as short entries are just the ones that often leave you wanting to know where to look for more. In the room these cuts have created, in come 119 of the REP's full entries on the people and concepts students will want to know most about, and 24 detailed subject overviews.

Better, then. But good enough to rival the Oxford Companion? Overall, the quality of the entries and contributors in both books is very high, and without having compared every page, it seems there is little to choose between them. And on several counts, the Shorter certainly gives the Companion a run for its money. No subliminal drug message intended, but take 'e' as an example. Emotivism, Equality, The Problem of Evil and Existentialism are all core subjects students and enthusiasts will want to know about, and the Shorter's longer entries deliver more than the Companion's. The long biographical entries on the most important philosophers are particularly welcome. And the Shorter still has a wider global reach than the Companion. If you want to know about East Asian Philosophy or Indian Schools of Epistemology, the Shorter enlightens where the Companion leaves you in the dark.

However, the ultimate test of any reference book is whether you can quickly find the information you need, and in this respect the Shorter comes up short. It's not just that it has "well over 900" entries compared to the new edition of the Companion's 2,300. That may reflect no more than the Companion's tendency to chop up its subject matter into smaller pieces. The problem is that the Shorter combines fewer, longer entries with no index. So, for example, it actually has more to say on 'elenchus' than the Companion, but unless you already know where to find it (in Socrates), you're stuck. And the whole point of a reference book is that you don't need to already know about something to look it up. In contrast, the Companion boasts a comprehensive index as well as more individual entries. The result is that you can almost always find your way to the information you seek in seconds.

So if I could only have one single-volume philosophy reference book, the Oxford Companion still has my vote. Nevertheless, the Routledge Shorter Encyclopedia, because of its different strengths, still deserves a proud place on the bookshelf of any philosopher lover. It fills the few holes in the Companion's coverage and provides greater depth on many subjects. But without an index, Craig's splendid source material has once again been short changed. Not by much, mind, which only makes it more frustrating.