I don´t know if Mongoose thinks the same, but for me RuneQuest is nothing else, than another BRP game.
If you are a BRP fanatic, and DON`T have any/much of Mongoose RQ line until now, the SPECIAL BUNDLES of The Chaos Society may be for you:
eBay Seller: rashoran: Toys Games items on eBay.co.uk
Here you can get BUNDLES of RQ books for a good price.
Cheers
André