The library, which has eight properties in London, including the £511m St Pancras building and a 43-acre site in Wetherby, North Yorkshire, added that it might build or rent new properties.
Ruth Coman, head of estates at the library, said the review was required because of the library had to find room for more and more books – it has to house at least one copy of every book and magazine published in the UK.
She said the move was also in response to the St Pancras building's being fully operational after its opening in 1997.
Coman said: "We have bedded down in St Pancras. Some of the problems we had on the site have been sorted out. What we are looking at is making sure that we have the right management structure and contract structure for our whole estate to take us forward to the next decade. We are taking stock right now."
Coman said none of the buildings, apart from St Pancras, had proper air-conditioning to safeguard the books. She said: "Some of our portfolio is fairly low quality rented accommodation. In our Wetherby site, there is a mixture of Portakabins and old munitions factories."
Industry sources said the M&E work for the library, now carried out by Emcor Drake & Skull, would be the most lucrative of any retendered contracts.
One source said the library was considering an M&E and project management deal that would last for five years. He said: "It will be a multimillion-pound deal. Keeping the books in the right condition is a sensitive job."
The St Pancras job, designed by Colin St John Wilson, had a troubled history. Design work started on the project in 1976 and the construction phase was beset by technical and legal problems, including a failed £9m claim for faulty wiring.