And, it comes as no surprise that it is one of the most popular tourist attractions in the county.
On top of thousands of books that are on display, there is also a selection of precious books that are locked away, the most expensive valued at £16,000.
To celebrate World Book Day, we wanted to show you round the biggest book shop in the area.
Here are nine pictures of what to expect if you visit:
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Take a look inside one of Northumberland's most popular tourist attractions. Photo: Charlie Watson
. Thousands of books
Although it's no surprise that a book shop sells books, Barter Books has thousands of books up for grabs. The whole building is lined with novels, short stories and historic books. Photo: Charlie Watson
1. Thousands of books
Although it's no surprise that a book shop sells books, Barter Books has thousands of books up for grabs. The whole building is lined with novels, short stories and historic books. Photo: Charlie Watson
2. Records
There's more than just books up for grabs in Barter Books. Second hand records from music legends can also be picked up. Photo: Charlie Watson
3. Pricey books
Despite the most expensive books being locked away, there's still an array of pricey books on show. One of the most expensive books is £13,600. Photo: Charlie Watson
4. Old Waiting Room
And, what better place to tuck into a new novel than in a cafe. Barter Books has its own cafe which serves cuppas, cake and meals. Photo: Charlie Watson