I found this in the children's section of a library probably in the vicinity of the year 2000 or so, and have not been able to find it since.
The book was illustrated (with watercolor?) in a style similar to that of William Steig. It takes place in a world of mostly anthropomorphized animals, but including humans as well (I think). The title was a single word (the main character's name, I think), and was something like "Ivanhoe" (but that was clearly not it) or had a similar cadence to it.
The plot, as I remember, involved a snake who was somehow accidentally(?) transformed into a man via magic (by a kindly wizard?), and proceeded to have adventures.
One that I remember was that he met a creature (a rat?) who was a painter who painted incredibly realistic paintings, and asked the creature what the point of creating such an exact replica of a real scene was, and the creature replied something like "there is value in being able to see an image of spring when it is winter, or vice versa".
Eventually, the man met a woman, fell in love, and somehow confronted an evil wizard to rescue the woman. The evil wizard, in an attempt to curse him, transformed him into a snake again, not realizing that this was actually his native form and therefore not the inconvenience that the wizard imagined, at which point he overcame the wizard and rescued the woman.
Does this sound familiar to anyone?