Upvote:2
"Best" is relative. However, I'm quite happy with Turdus for Wikitravel and Wikivoyage for, you've guessed it.
Both are fairly usable and work offline. And they're free.
I also recommend mapswithme, for offline maps. There's a free version and a paid version which also allows you to search the maps, which is super useful (I'm not affiliated).