What do you buy for a bibliophile?

I’m in a happy position, but it’s complicated. I’ve got a *massive* book voucher to spend on anything I want. But what do I want? Not novels… I already own many hundreds more than I will probably ever find the time to read, and I have access to the even more substantial fiction collections of various family members. I want to spend my loot on something meaningful, and so this morning I’m pondering what exactly are the fundamental texts that any medievalist worth her or his salt ought to own. I already have my own copy of Lewis & Short’s Latin Dictionary – a lucky find on the Blackwell’s second-hand shelf about a decade ago; I own Latham’s Medieval Latin from British and Irish Sources; I’ve got one and a half sets of Tout’s Chapters in the administrative history of mediaeval England, and both medieval volumes from the English Historical Documents series; if you’ve been reading closely you know that I recently acquired Powicke on King Henry III and the Lord Edward, and I already have his The Thirteenth Century — another lucky second-hand find in York a couple of years back; I’ve also got both the earlier and later medieval volumes of the much more recent Social History of England, and a miscellany of royal biographies… In fact I have four full-height bookshelves of assorted medieval ‘stuff’, but I’m sure there are things I don’t have that I ought.

What would you do? Get something shiny and new, reflecting up-to-date scholarship? Or invest in the big reference tomes like the New Cambridge Medieval History? Primary sources? Readers for undergraduate teaching ideas? Specialist works? General surveys? What are the indisputable must-haves on your list? I need some inspiration, because for some perverse reason it’s much harder to know what to do with windfalls when they fall, than it is to dream about what you would do with the money when you haven’t any!

[Edit: it turns out it’s quite difficult, nay, impossible, to get second hand volumes through this outlet, so we’re looking at stuff that’s still in print on this occasion, folks…]