The theft of the books has been linked to a Romanian crime group. London's Met Police said the books were found in a hidden compartment under a house in rural Romania.
About 200 rare and valuable books worth 2.5 million pounds (€2.7 million; $3.5 million), which were stolen from the UK in 2017, were found buried in a house in Romania by local police on Friday.
London's Met Police said the books were unearthed in a hidden compartment under the house in Romania's Neamt county.
"These books are extremely valuable, but more importantly they are irreplaceable and are of great importance to international cultural heritage," said Detective Inspector Andy Durham of the Met.
Some of the books and works unearthed include first edition works by Galileo Galilei, Isaac Newton and Dante Alighieri, and sketches by Francisco de Goya.
The works were stolen from a warehouse in west London in January 2017. Burglars cut holes in the roof, dodged motion sensors and then stole the works before they were set to be auctioned in the United States.
The UK's police said the theft was linked to "a number of prominent Romanian crime families who form part of the Clamparu crime group with a history of complex and large-scale, high-value thefts."
Police from the UK, Romania and Italy conducted a joint investigation that included two EU agencies to identify 11 similar burglaries across the three countries.
The joint investigation led to the netting of around £2 million ($2.6 million) worth of property and the arrest of 13 suspects, of which 12 have already pleaded guilty.
am/sms (AFP, AP)