Just like a good costumer can not depend solely on art, a food historian can no solely depend on cook books to understand food, cooking or dining through history. I will say now, if you do, you will be missing a large part of the picture.
Now, keeping in mind that I'm somewhat focused on some areas more than others when it comes to culinary history so I miss a lot of stuff, but some things remain the same, and this is how I compile information.
Cookery books are a good place to start, here we have period accounts, contemporary to what ever period we are studying, of direction on preparing, serving and sometimes description of the food and ingredients to dishes we are trying to re-make. We can even compare with recipes both before and after and see trends, but we are only getting a portion of the picture from this.
Another source we have available is art. Here we can often find pictures of food being prepared, served, sold and so on. Of course this is best pared with collected written information. Sources I don't rule out when looking for artwork are, but not limited to, prints, paintings, illustration and carvings from the era.
Actual food and food preparation antiquities, and with this, any info taken from them. This is the actual thing! but to make use of it, the last two items come in handy in order to put it all into context.
Food related writings and writings with food related items: Notice I have been posting transcriptions of animal husbandry books? Those are just one of many sorts of books related to food production. We also have books on grains and farming in general, milling and factory production and so on. We also can find various accounts in fictional and non fictional literature written in the period, basically items of text describing parts of common domesticity, it's valid... look at how many people refer to Chaucer for food description, it's because it placed it as an everyday known item into his stories.
That said, there are even more places to look and rocks to overturn....
as a parting gift, here is a pinterest page I made up of various images of Cooks from the medieval era to the 17th century: http://pinterest.com/landverhuizer/some-medieval-cooks-along-with-a-lot-of-16th-and-1/