The first thing that you should know about Robert Heinlein's "Farmer in the Sky" is that it was written on commission from the Boy Scouts of America - they commissioned him to write a story about establishing a Boy Scout troop in space. Between that and the publication date in the 1950s, you can pretty much get your expectations straight - the book has a definitely sanitized feel and at times feels like it takes its diction directly out of an episode of Leave it to Beaver, and people who aren't tough or naturalistic or willing to sacrifice their amenities or their sense of privilege are presented frequently as overblown caricatures, clearly present for derision.
The book is further plagued by rather massive pacing issues. In particular, a section of the book in which something extraordinarily important is not given any lead-up, is then stated matter-of-factly in a single paragraph rather than described through narration, and is mostly ignored thereafter. I won't give anything away, but suffice to say that shit like this should be treated with more depth.
So, why bother with "Farmer in the Sky" at all? For one thing, the hard science fiction aspects are quite interesting - in particular, Heinlein paints a picture of the alien landscape of Ganymede as being a hybrid of a world completely unlike Earth - as all worlds that aren't Earth should rightly be expected to be - and Earth itself. It's similarities are really what make it feel so different. This is very well-executed.
The other thing is a rather brief section near the end in which one of the characters discusses the idea that Earth is heading towards a cataclysmic war due to overcrowding. That particular section was pretty thought provoking - exploring the idea of how human society reacts to its own overwhelming growth.
Ultimately, "Farmer in the Sky" is not a great book. It's not even a really good book. It does have a couple of thought-provoking sections, but those are pretty tough to reach for all but the most dedicated classic science fiction fans. If you're a big fan of the Golden Age sci-fi greats and want to check out a lesser-known pulp by a well-known science fiction author, I wouldn't rule out "Farmer in the Sky." All others need not apply.