If you find yourself in South Korea and are looking for books you will find that bookstores in South Korea do not disappoint. Although Korean is the main language there is no shortage of Korean citizens that speak English in some beginner to fluent level. This does vary from city to city, starting with Seoul as the most fluent to small cities being the least fluent in English. However, any bookstore you visit will have an English section.
Kyobo is by far the best bookstore when it comes to English books availability. You can find Kyobo in most cities on the peninsula. They provide website access and same day to next day delivery if you are avoiding the covid crowds. If you feel like taking a break from staying in, you can walk into one of their locations and you will find that it also conveniently has a stationary store and many of them have cafes for you to enjoy some reading. When inside the bookstore you may read some pages or the whole book if you are inclined to. Most Koreans are respectful and treat bookstores the same as libraries; everyone keeps a low voice and takes a seat wherever possible.
Next is Youngpoong Books stores or YP Books for short. These are similar to Kyobo bookstore, they provide a wide range of book selection. They have stationary stores and toys for kids within their vicinity. Some are large enough to cover two to even three floors of good old entertainment. You may find people during their lunch stopping by to read for a bit. You may also catch a few young kids after school browsing for some manhua (만화) or for some magazines. There is absolutely no shortage of school practice books starting from the first to 12 grades. You will also fide a wide variety of English books and Korean learning books.
Aladdin Bookstore is a second-hand bookstore. If you are on a budget this is the place to be, however, some locations have proved to vary on the number of English books available; if you chose to go into an Aladdin bookstore expect to find a small variety. They offer merchandise and DIY crafts for decent prices aside from books. They have a small section for music albums for reasonable prices. You might not walk out with an English book but you will walk out with some sort of craft or entertainment goodie.
If you do not want to leave your home due to the pandemic, you can order online. All major bookstores have delivery options. There also major commerce services like Coupang, G-Market, and Interpark.
There are many small bookstores through out South Korea but the small locations rarely have English books available. Unless you have mastered the Korean language, I would say head to your big bookstores to find your much needed companion. Cafes are in no short supply in South Korea, they are as common as convenience store. So, grab a book, get yourself a cup of coffee, and take your mask with you. Enjoy the view and ambiance of a country that has embraced the wonders of slowing down to catch up on some reading.