There are a lot of coloring books related to Alice in Wonderland and there is almost every possible artistic style you could want. They vary from rather easy to color to rather difficult to color in. The coloring books with Tenniel's artwork are quite difficult to color in since his art is so dense in nature that coloring entire areas is about the only option.
Another thing to consider in getting coloring books (of any kind) is whether the art is printed on one side of a page only or on both sides of a page. If it's on both sides then you have to be careful about possible bleed-through from one side to the other.