How many errors have snuck past you in editing? No author can get through an entire book without making a mistake (and I personally can't seem to get through a single paragraph without them), but it's not entirely your fault. Words are confusing, and they have lots of different forms that only adds fuel to the fires of bafflement. But if the wrong usage of a word sneaked past you in the past, you can prevent it in the future -- just learn which one's right. In the epic battle of sneaked vs. snuck, which word will win?
Sneaking in the Past
By and large, books are written in the past tense. Some authors do create their books using present tense, but past tense is the most popular...and this makes it difficult to chose the right word forms. Words like sneak, which have more than one past tense form, really only exist to make your job difficult (that's my theory, anyway).
So, which one's right? Both of them. Whether you're using sneaked or snuck, either can be used in your book and remain correct. Sneaked is older; it's been in use for about 5 centuries. Snuck originated in the United States only about a hundred years ago, but in the past century it's spread to all English-speaking (and English-writing) countries. You can find either word in major, prestigious publications and popular books around the world.
Some traditionalists, however, absolutely hate the word snuck; it's still too new for some of the old school grammarians. But if you're writing ebooks, I say embrace any and all word trends. No word that's over a century old can be considered "new" when dictionaries are updated every single year.