Lonesome Dove is a story about a pair of retired Texas Rangers and several characters connected to their lives. The Rangers drive a herd of cattle from Texas to Montana, undergoing a series of harrowing adventures as they do. The novel deals with themes of friendship and privation, with obstacles such as outlaws, stampedes, and hostile native populations barring the ex-Rangers from their goal in Montana.
Boasting the largest collection of book summaries, BookRags is the best option for titles you can't find elsewhere. They offer all of the basics (quotes, chapter summary, characters, historical context, literary criticism) but also walk through a few major topics that recur throughout the book, which can be particularly useful for essay writing.
Their book summaries aren't as good as other providers, but PinkMonkey often has interesting insights that aren't mentioned elsewhere on the Internet. For example, they go over literary elements (like setting, conflict, and mood), compare and contrast, and symbolism/motifs. It's a good site if you want to find a unique fact or angle that other students don't know about.
Includes the standard sections found in most book notes, including a book synopsis, chapter by chapter analysis, author biography, character list, essay topics, book report ideas, and study questions. This website is less comprehensive than other book notes sites, but could be useful if you're looking for a quick review.