The most powerful books are the ones that change public policy, which was the case with Upton Sinclair's The Jungle. Sinclair was a journalist who spent 7 weeks working undercover as a labour hand in the meat packing industry and wrote this novel when he came back.
The conditions depicted in the novel are deplorable. Both workers and animals are treated extremely poorly, leading to an unsanitary American food supply. The novels follows an immigrant protagonist in the early 20th century who tries to make his way in the New World, but meets tragedy after tragedy. If you're looking for a pick-me-up, don't read this book.
That Sinclair is a socialist emanates throughout the book. Some of his gripes are legitimate in my view. The employers cooperate rather than compete with each other (trusts! e.g. Standard Oil), which allows them to keep wages low and blacklist those who would try to improve worker conditions. Government and police corruption is rampant, as those with money are able to buy votes/power/influence.
On the other hand, there were also some situations that didn't quite fit in with Sinclair's narrative. Despite the horrendous working conditions, there were able and willing unemployed workers a mile-long at all times. If the working conditions were so bad, why were there so many people wanting this work? These jobs must have been better than whatever alternative (farming?) these unemployed workers faced that drew them to these employers.
There is also little emphasis on saving. The workers do go through some times of plenty, but they spend everything they make. When the boom times end, they've got nothing. Sinclair seems to see this as poor treatment of the workers by employers, but I don't, as the employers aren't making anything either (and may be losing money) when times are bad. If Sinclair's characters spent less on booze and women during the good times, they would probably be alright during the bad.
The characters' obsession with home ownership also proved to be a problem for them. They could have lived much more comfortably as renters, but emotions (and some silver-tongued sellers/agents, to be fair) got the better of them and they bought a place they couldn't afford (and subsequently lost). Some things don't change I guess, as the housing crisis demonstrated this human motive to be alive and well.
Finally, Sinclair clearly sees the economy as a static pie, and believes that its slices should be more fairly distributed. So it's not a big surprise that innovation/entrepreneurship played no part anywhere throughout the novel. Every worker is looking to find someone who needs an employee for an existing mundane job, rather than trying to actually add value by coming up with new things that might actually grow the pie for everyone.
But of course all of this is easy to say from my perch. I've never had to face anything like the harshness these people were confronted with. Though my parents arrived here as immigrants without much, they did not face conditions anything like this. I think it's an important read for anyone who wants to understand what can happen when competition is kept low (whether that monopoly is through government or the private sector), and why we have some of the regulations we do. They may not all make sense in today's improved conditions, but they're probably there because someone abused their power and made the regulations necessary at one time.