This book, the children's introduction to Middle-Earth by J. R. R. Tolkien, is a straight-up classic. Before diving into description of or reflection on it though I will just hazard to say that the edition linked there is virtually* unillustrated - which for me would be a deal-breaker as the version I have is fully and beautifully pictured by Alan Lee, that veteran Tolkien illustrator.
Often described as a prequel to the Lord of the Rings trilogy, I think this description is as unfair as it is inaccurate - Tolkien wrote this first, after all - as it, as a story, has completely different aims in mind to its more epic successor. The Hobbit was written up after its various elements had emerged from bedtime stories Tolkien was making up for his kids, and it kind of shows. Not in a bad way, just in the sense that it feels quite episodic in places - the natural breaks being of course "no, that's it for tonight, you've had nearly two-thousand words of story, now go to sleep Christopher" - and the prose is somewhat whimsical, juvenile in places even.
Brief overview of the story then - spoiler warning, if that needed to be said. Bilbo Baggins is a hobbit, who lives a quiet comfy life. Until, that is, a wizard called Gandalf comes round, and invites a dozen dwarves to his home for tea. Bilbo is not happy about this. It transpires that Gandalf and the dwarves (who are led by one particularly stern dwarf called Thorin) are planning a heist to recapture their ancestral kingdom from the dominion of a dragon called Smaug; and Bilbo is to be their party's burglar. Despite the notion of this adventure terrifying him at first, our eponymous hobbit acquiesces and finds himself soon leaving home with the wizard and dwarves. They have a short altercation with a trio of trolls, find a bunch of cool ancient weaponry, and continue into the mountains; however they are soon captured by goblins. Gandalf rescues them, but as they're running away through the mountain tunnels Bilbo falls down a ravine and becomes isolated. He finds a ring on the floor then meets a strange creature called Gollum, who lives in an underground lake, and, as is promptly made clear, wants very much to eat Bilbo - the pair have a contest of riddle-telling/solving, which Bilbo wins** when Gollum can't guess what's in his pocket (i.e. the ring). Gollum then decides to use his magic ring (same one as Bilbo has found) to turn invisible and eat the hobbit anyway, but Bilbo - no prizes for guessing this - uses the magic ring to turn invisible, and escapes. Meeting back up with the dwarves and Gandalf outside, the party evade goblins and wolves by the skin of their teeth and then go to visit a man called Beorn who can change into a bear. After this hospitality, Gandalf leaves them for business of his own wizardly kind, and the dwarves with Bilbo travel to the great forest Mirkwood, where they get lost, then captured by spiders, then liberated by Bilbo, then captured by elves, then liberated again by Bilbo (who is making great use of the ring by this stage). After escaping prison, they make their way down the river (quite literally, in barrels) to Lake Town, near the mountain where Smaug lives in the dwarves' old home with a shit-ton of treasure. The human inhabitants of Lake Town have mixed reactions to their arrival; some recall prophecies that when the dwarven king returns to take his throne prosperity will greatly increase in the region, while others think their meddling will just result in Smaug causing a load of carnage. Next, our party creeps up to Smaug's lair and Bilbo manages to sneak in through a secret door - once inside, and invisible obviously, he has a brief conversation with the dragon, and also manages to find the Arkenstone (a gem of immense value to Thorin), before sneaking back out. As the folk of Lake Town feared, it all does indeed backfire, and Smaug goes on a fiery rampage of destruction, until he is killed by an archer called Bard in something of an anti-climax. The dwarves' troubles aren't over yet though - once inside the mountain Thorin succumbs to "gold-madness" and gets very cross that he can't find the Arkenstone, while armies of goblins and wolves are drawing near, and an army of elves seeking revenge for the dwarves' jailbreak arrive and start asking for a share of the treasure (as apparently a fair bit of it was plundered from them by the dragon). Thorin gets increasingly paranoid, so Bilbo gives the Arkenstone to Gandalf and the elves for a bargaining chip. Then the evil armies arrive, there's a huge battle, Thorin is wounded badly, and dies after forgiving Bilbo; then all that's left to do is take his share of the treasure and travel home.
In terms of my own reflections on it, I don't really have anything profound or even interesting to say - I just think this is a rollicking good story, one that entertains adults just as much as children, and breathes life into a fantastical world in ways few writers*** can pull off. Would of course highly recommend to anyone with a love of imaginative fiction, especially if you happen to be under the age of about twelve. Like, I first read it when I was six, and other than Gollum scaring the shit out of me I loved it to bits.
* I say "virtually" because it does in fact have nine black-and-white illustrations, as well as two maps, by Tolkien himself - but my edition has well over fifty full-colour illustrations as well as those original maps, so...
** One of the biggest injustices in Tolkien's whole canon, if you ask me. Never mind the fact that "what have I got in my pocket" is definitively not a riddle, if only Bilbo hadn't found the ring or even better given it back to Gollum when he realised it was the poor creature's property then Sauron would never have got wind of it and the wars at the end of the Third Age wouldn't have happened.
*** And even fewer film-makers - I mean, have you seen Peter Jackson's Hobbit trilogy? The first one is okay, but the second two are utterly awful - overall it falls so far short of Jackson's prior work on the LotR trilogy that it almost beggars belief. I mean, the main mistake was their need to make it into a trilogy at all. It should have been one single two-to-three hour film with Guillermo del Toro at the helm; and it should have retained the child-friendly fairy-story tone instead of selling itself as a tonal and narrative prequel to LotR - just - eurgh. Martin Freeman as Bilbo though was inspired casting.