If you are familiar with the Redwall series then I'll jusy say it as good as any Redwall book; and better than some of them because the main character is slightly out of the mould for a hare. But all the core values that Redwall has taught us to value and emulate are as strong as ever.
If you aren't familiar then by the book that started it all - Redwall. Follow the series if you like it and by the time you reach The Sable Queen; you'll be well-placed to decide for yourself if it is a worthy addition to the series. You won't lose too much if you jump in and buiy this one first, but it will add so much more to your experience of the Redwall world if you start at the beginning.