The turbulent middle period of the Anglo-Saxons (around 800 AD) was plagued by frequent Viking invasions as well as internal tribal conflicts. We started with books and articles in history magazines:
We attended a lecture held at an university about warfare, medicine and development of the modern English language from the Saxon language which intermingled with the Old Norse language and finally developed into Old English.
The greatest English king of all, and the only one to be called "The Great", was Alfred of Wessex. We learnt about him from various folklores about King Alfred's Cakes (a type of fungus), and from various documentaries, most notably an old documentary from Michael Wood. We also found a more recent and generic but detailed introduction to the Saxon period by David Starkey to be very useful: