Hmm, tricky one. I think it depends entirely on your tolerance for a very specific, deliberate pace. I read 'Lonesome Dove' itself, obviously a masterpiece, and felt so satisfied I tried the prequels and sequel. Honestly, the story feels complete with just the first book. The others are well-written but sometimes feel like footnotes or expansions, lacking that central epic sweep. 'Streets of Laredo' in particular is a real downer, shifting tone drastically. If you’re deeply in love with the characters and just want more time in that world, sure. But if you’re hoping for a continuous upward climb in quality and feeling, you might end up a bit disappointed. It’s a case where the original cast a shadow too long for the rest to escape.
That said, 'Dead Man’s Walk' and 'Comanche Moon' offer interesting backstory for Gus and Call, showing how they became the men they are. I didn’t regret reading them, but I don’t revisit them like I do the main novel. They fill in gaps rather than create new, self-contained magic. So, worth it for completists and mega-fans, but for most, stopping after the journey to Montana is a perfectly valid and maybe even optimal choice. The sense of loss I felt finishing 'Lonesome Dove' wasn’t really cured by the other books, just… extended.