I'm doing a project about a historical figure's personal library, and in writing about the origin of books I am trying to find some sources on how common book ownership was among lower socioeconomic status individuals in Britain, especially between the end of the Middle Ages to the 20th century. This historical figure was an Englishman who was quite wealthy and lived in the United States for the majority of his life. I know this is very vague, which is why I've been having a particularly tough time finding a potential source. Any input would be appreciated.
Awesome question! Book ownership is something that wasn't well tracked. If your guy (if he was real) had a bookplate, you might be able to start there. So maybe we should explore if it's feasible he (whom I am calling HF from now on) had access to buy books.
The timespan you mention is HUGE; I'll try to touch on all of it. So one of the things that marks the end of the "Middle Ages" is the invention of the printing press, which was in 1440ish. Obviously printing made books much cheaper. In the 1500s we still get a lot of plays and a continuation of the medieval epics a la Handbook of a Christian Knight. Since most of the literacy remained in the top eschelons of society -- schooling was expensive and took you away from your work -- HF was probably not buying books unless it was really a strong hobby because he probably could not read.
But you mention HF lived in the US extensively, so your target date must be somewhere from the early 1600s to today. (By US, we'll just cover white europeans settling in North America.) In the 1600s, lots of plays were produced and their manuscripts would have been printed. The average Joe probably wasn't buying these, but the local Earl or Duke or Guy In The Big House In Town was. If HF is a friend of one of those guys, he could have had access, but probably not a copy of his own. Some glorified book clubs and subscription libraries emerged, but this was mostly upper middle / upper class affairs, but free libraries did not exist yet.
In the 1700s, the first real novel was produced in Robinson Crusoe (but don't worry, we only say that when Cervantes isn't looking.) Novels became super popular, but they were mostly considered women's books. Men were mostly reading Pope-esque poetry, Swift-esque satires, histories, and books with a science bent, or something like The Complet Angler (although it was published in the 1600s) and guide books to assist their travels.
Circulating libraries (w/ small fees) first popped up in the 1720s, and this gave access to affordable books for the middle class. People were reading Swift, Pope, Defoe, Richardson, Gulliver's Travels (1726), Pamela (1740), Tom Jones (1749), among others. In the middle of the century in America, Ben Franklin started the first completely free libraries. If ever HF cultivated a book reading habit, it was the 1700s, but he probably didn't have too many books of his own.
If he's a servant, its likely he could not read up until the late 1800s when school (and learning to read) became mandatory.
Characters in Jane Austen's novels (early 1800s), which are typically upper / middle class women, are often discussing novels and important british authors with a certain amount of familiarity. In the late 1700s & 1800s, pamphlets become very popular because they were so cheap to buy. Additionally, "serials" -- novels printed in magazines or "part issues" one chapter at a time began in the 1830s, and were became hugely popular because they were very very cheap.
The best way to research if your HF might have owned books would be to look at the ledgers or wills of other people from the same time and background as your HF and see how many books are listed. Additionally, in the specific time you're in, what was being sold that your HF could have afforded? Newspapers would advertise books and their prices.
Best of luck.