I have read the occasional bibliography in an Ars volume , but not recently.
The 7 books i do have:
4 by Frances and Joseph Gies:
Life in a Medieval (Castle , City , Village) & Cathedral , Forge , and Waterwheel. G.G.Coulton: Medieval Village , Manor , and Monastery. Sherrilyn Kenyon:
The Writer"s Digest Character Naming Sourcebook (1st Ed)
The Writer's Guide to Everyday Life in the Middle Ages.
Some of the books listed in a bibliography are either way too costly (more than $100)
or only available from a university library.
I did find the Gies books an easy read and managed to plough through the Coulton.
As i alway have trouble with creatively endowing names or recalling Etiquette , often refer to both Kenyon books.
And just to plug Atlas Games ,
i have used Once Upon a Time (2nd Ed)
quite successfully in other rpgs. My Ars players have so far resisted any temptations of Faerie.
(Having just checked the link , i find two expansions to buy.) No-one told me
Any lists of books , comics , dvds, or whatever that people care to share will be muchly helpful.
Foreign language dvds are ok as long as they have English subtitles.
Not strictly speaking history books, but I have gotten a lot of inspiration from the Brother Cadfael mystery series by Ellis Peters. Centered around mystery solving Benedictine monk in mid 12th century Shrewsbury, during the Anarchy, these novels give lots of good examples of how real historical events and people can be woven into fictional stories without the history dominating or even being the main focus of the fiction.
The Cadfael Collection (1995) ; B00068RYZU (for the search) ,(the amazon url is too long)
At US-$135 , this is a lot more than i recall paying for the set i got from the UK.
Cadfael - The Complete Collection - Series 1 To 4 [DVD]  ; B0002475S4 from Amazon UK is the one i own.
B002EAKWES for the collection that is actually in stock for £17.99
The books appear to be much cheaper in the UK as well.
Generally books of Fairy tales or spanish Mythology (diffficult to find about Castillian and on Spanish, there are more about Asturia, Basque Country, Catalonian and Gallaecia), i think that a dictionary about Knightly stories should be great; but i found one:
"Mitos y Leyendas Populares" Collection "Letras Españolas" Written by José Calles. Editorial: LIBSA
After of that ther are a collection about floklore supernatural beings:
"Guía de Seres Mágicos Españoles" Three tomes: "Duendes, Hadas y Gnomos", written by Jesús Calleja. There are other book about Child Terrors that i did'nt find it.
And a book about the mysticals and common aspects of the Crafters, smiths, agriculture priests and alchemist of Mircea Eliade.
Set in Exeter (and Devon) in 1194, John is the County Coroner for Devon,
The books are entertaining and (to my eyes) seems pretty accurate (I live just outside Exeter, and he's clearly done a lot of research into the region - if nothing else, the books contain a good map of the city for 1194). Good information about how the city works and politics (both with the sheriff of Exeter and with the church, as well as how the county coroners position is supposed to work),
And, well, it's cool seeing local places getting name-checked
I find non-medieval books more useful. Books about non-European (and non-Medieval) cultures, science fiction books, literary fiction. You can get heaps of good ideas about exotic magic, and interesting characters and situations. Non-fiction (and fiction) set in the medieval period tends to be a bit samey and predictable. Source material from a totally different context can be very inspirational.
Tales from the Green Valley Down on the Farm - 1620’s style
How do you gauge gas mark 7 when you’re using a 17th century bread oven?
Why did people 400 years ago save up their urine to help with the laundry?
Why did farmers in Britain traditionally plough with oxen and not horses? Tales from the Green Valley , the official site.
While not the 1220s , there is enough here for those who like the minutiae of domestic life.
You could also use the people as templates for covenfolk.
I've read several books over the years because I thought that they would improve my Ars Magica game. Most of them I found dull and inadequately applicable.
These three however I thought were excellent, but perhaps this is just because I'd finally absorbed enough history to make the connections that the authors erroneously assumed any possible reader would know.
But the one book that I kicked myself for not reading earlier was a medieval history textbook.
A few years ago I picked up my wife's old textbook from the basement bookshelves and I was blown away. Here, laid out in preposterously simple readable English, was everything that I had wished someone had told me and all of the information that the other authors had assumed that I'd know already. My advice is go find a book designed for medieval history 101 and was designed to engage lusty, distracted, short attention span, 19 year old kids who are really interested in getting a degree in music or engineering and see the class as a hoop to jump through rather than an opportunity to learn and then read this book and benefit from the great effort that the authors have gone through to make the subject accessible and entertaining.
Cadfael to give some ideas, as well as other historical novels
several books on middle age, such as God in the middle age, children, etc.
book of greek mythology, books on mysterious regions such as Brittany, whole France, Corsica... to get places which may be faeric, magic, divine, infernal, to find places where to build alliances,...
If looking for suggestions for which particular book, have a look at your local university's introductory medieval courses. The university should probably have information freely available (on the web?) on the set texts for the courses, and if it is a university course text you will be bound to find cheap copies in your local second hand bookshops.