My younger son (now 8) has loved--and I mean loved--the Redwall series. He has an anthropomorphic mouse fetish, and has always loved books with this type of character. Anthropomorphic mouse, in fact, is something of a genre onto itself in children's literature, at this point.
The first thing to know about Redwall, should you think you might tackle it, is that it is really really long. The sheer bulk of Redwall is jaw-dropping. In fact, it hard to imagine so much prose, so narrowly focused, being generated by a single human being. How many pages? Well, let's put it this way, if you stack up all the Redwall books, the word count exceedes that of Harry Potter, the Lord of the Rings and Narnia--combined.
How does he do it? Well, for one thing, there's no dependency between the books, each can be read separately. The relationships between the novels is almost purely generational. Starting with Redwall, and leaping back and forth generation by generation, Brian Jacques fills out his furry medieval history. Youthful protagonists of one novel may be the grandparents of the protagonists of in the next, chronologically in the series. So there aren't really casts of recurrent characters, as much as there are archeatypal roles which are played out frequently by the same types of animals in book after book.
There's the badger mother, who raises many of the young orphaned animals. There's the quest-mouse, often the protagonist. There's the spirit of Martin, the abbey's protective totem, who guides the quest mouse. There are the warrior hares. There's the badger lord of. Salamandastron
Jaques rules for epic fantasy are familiar to genre readers, but he adds a few additional rules to the mix, making Redwall both unique, and, somewhat less...unpredictable, than a lot of epic fantasy.
1. Technology ceases before firearms. The trappings of high fantasy are ruined by guns, grenades, artillary. Redwall's walls become meaningless when canons can batter them down.
2. Certain races are evil. Certain races are good.
I hate to be PC about this, but this aspect of medieval fantasy is a bit troubling, and Redwall's tremendous popularity with the very young makes this doubly suspect. With the exception of a single sympathetic pirate rat in one of the Redwall novels, there isn't a single example of a member of an 'evil' race transcending his racial stereotype. Or of a 'good' race failing to be good. Mice, shrews, Voles, squirrels, otters, hedgehogs, badgers, hares, (there are no average rabbits) are good. Rats, wolves, foxes, stoats, pine martens, are evil. Omnivores and Herbavores are good. Predators are in general, evil, though the few exceptions provide some moments of interest. (Cats are handled carefully, with a pair of royal twins, one good, the other evil.)
3. Domesticated animals don't exist. (but somehow, Milk does.)
There are no dogs, housecats (the cats mentioned above are wildcats) horses, cows, goats or chickens. So while there are sentient animals (anything mamallian) and non-sentient animals (fish and bugs) which can be safely eaten, we don't ever see the people-animals treating other animals like...well, animals. Omnivores eat fish ethically; bad races like to roast birds. (Many birds are quasi-sentient.)
4. There is no magic but destiny.
Jaques is careful to point out that power emanates from the individual--not his magical gear. Certain magical items 'find' their owners, and are wonderful tools, but they don't make their owners powerful in and of themselves. Destiny, in the form of prophetic writings, carvings, poetry and dreams, the dead returning to advise the living, and a great wall carving which seems to record all history past, present and future, are the series only magic.
5. Good characters cooperate. Evil characters backstab. Evil is punished. Good prevails.
We don't need to explain this one, though Jacques vacillates on the nature of just punishment. Do groups of 'evil' races need to exterminated down to a single beast, or, do their leaders need to be executed and the remainder banished? Different books answer this question differently. Evil characters Kidnap. Evil characters torture. Good characters do not, but occasionally, good characters will slay evil characters _even as they are fleeing._ In the conclusion to Redwall, Mathias kills Cluny the scourge in a fashion that isn't strictly speaking, cricket, but most often, good characters play by certain rules.
Interestingly, even evil characters are bound by some rules. The use of fire as a weapon is a big no-no, which even evil characters often eshew.
6. Gender isn't destiny
This is a pretty cool aspect of Redwall, Though many normal gender stereotypes prevail, there is an abundance of powerful female warriors as well, including Mariel of Redwall, the protagonist of one novel.
Food is a huge aspect of Redwall (Jaques is French, after all) and approximately 1/4 of the words in any Redwall book are focused on cooking and eating. This is charming and lovely at first, but around book 3 or 4, you may find you've had enough of it.
This is the thing about Redwall--I don't think you're meant to read it all. Unless your kid is a precious reader, it's hard to imagine a kid staying in the cognitive zone these novels cater to long enough to get through them all. Even reading them aloud, at say, an hour a night, would take years. We're on the fifth book now, and I'd say, overall, it's as good as the first. In many ways, it's exactly like the first.
Many children's books are written at multiple levels, where there's a lot here for the an adult mind to chew on, as well as story elements crafted for young minds. Redwall isn't written in this way--it's written for children. I've found a few interesting nuggets to chew on as I've read the first 1500 pages of the series, but compared to something like say, Narnia, LOTR, Prydain, Harry Potter, it's thin on adult content.
So, reading it aloud is a gift to your kids. LIke watching Jerry Lewis movies with them. It's not a universal gift, like reading Charlottes Web or Stuart Little, or the Phantom Tollbooth.
My advice would be to alternate Redwall Books with other books. And don't feel like you need to read them all.