I'm currently writing a little article on the use of missile weapons in combat for /r/fantasy and /r/fantasywriters. Unfortunately, while there are many, many, many English language sources on the longbow's performance, manufacture and tactical use, I've found very little information about crossbows in any period. What I have found, such as the rate of fire of belt spanned century crossbows and their penetrative power compared with the longbow, has been proven false by modern tests^1. Frustratingly, along with incorrect information about the performance of crossbows, there has been a lack of information on how they were used tactically.
So, I've decided to seek help here. Does anyone know of any English language sources - either translations of primary sources or secondary sources - that spends any significant amount of time exploring the way in which crossbowmen were deployed in battle. Preferably such a source would examine the development of tactics in one area over time, but even a generalised overview would be handy.
I'm especially interested in battles where crossbows were properly deployed (i.e. the opposite of Crécy, where they were denied their pavises, unable to spread out fully and possibly were unable to properly load their crossbows due to the mud) against similar numbers of archers (foot or mounted on horse, it doesn't matter to me) and any detailed explorations of the Genoese and the way in which they not only fought, but the organisation of their forces and the politics behind their use.
^1 Videos by Tod Todeschini show a slow, deliberate rate of fire of 3 bolts per minute from a 300lb crossbow drawn using a belt and pulley system, while using a goats foot lever on a similar bow he achieved a rate of five bolts per minute. Separate tests by Andreas Bichler using reconstructed bows of ~300lbs and ~620lbs draw weight showed that the lighter crossbow performed similarly to several 75-80lb longbows used in other tests by different authors. This falls into the extreme low range of militarily useful longbows.
Have you checked the book list in the sidebar? I know there are at least two or three books there under the Middle Ages bracket which should give you some direction.
Unfortunately the tactical use of the crossbow has failed to capture the imaginations of English-language historians to anywhere near the same extent that the longbow has. My research was primarily on the technological aspect of the crossbow rather than its tactical use, so I haven't read everything on that particular subject, but what information is out there is frustratingly limited. The definitive book on the crossbow has yet to be written so you'll have to piece together your information from a variety of sources. Also, somewhat inevitably, Crecy looms large in any discussion of the medieval crossbow (whether fairly or not) and has a strong influence on any debate in the subject.
As you noted in your other post, Strickland somewhat ironically has the best account of the crossbow's use in general. I don't always agree with Strickland, but his account is probably the most general. There are, however, some very good studies of more specific instances of the crossbow's use. I'll post some references in a follow up post. Some of these works may be a pain to get access to, though, but if you have access to an academic library (or a local library with a good inter-library loan system) that should go a long way to helping.
If you have any specific questions I can try and provide answers/sources to those but crossbows are a tricky, and rather neglected, subject so some things are still a mystery to us.