The fourth of these compilations which brought together useful articles for (A)D&D players printed in now out of print issues of Dragon magazine, this would be really practical for dedicated players and DMs. 

Instead of having to dig through piles of back issues of Dragon (if you were even luck enough to have started collecting them far enough back in time to have the relevant article) in order to find rules for a certain class or rules for two-hand fighting, or handling your castle, you could just refer to a handy little “Best Of” which neatly set out some of the more useful bits printed in the magazine over the years.

With the upcoming release of Unearthed Arcana which would cover some of the same material, these Best Of collections would become a bit less useful and as such we will have a fifth volume but no more than that. Still, this would have been pretty invaluable at the time.