Hi there, I'm not entirely sure I'm in the right place for this but I'm feeling I want to learn more about the Varangian & the Swiss guards. General history and such. Sorry if I'm in the wrong neighbourhood.
Just to be clear are you looking for book recommendations about the Varangian and Swiss guards?
Well there are a couple primary sources I can suggest for you. The first would be Saga of Harald Hardråde in Heimskringla which details Harald's interactions with the Byzantine Empire Andrew his time with the Varangian Guard. For that the Viking Society for Northern Research's publications page does have a PDF online for Heimskringla (http://www.vsnrweb-publications.org.uk). The other source would be the Russian Primary Chronicle. It covers the history of Kievan Rus from the 9th century to the 12th century.
As for secondary sources there are quite a few interesting books. If you are looking for just a general look at the Varangians, I would suggest Peter Sawyer's The Oxford Illustrated History of the Vikings. However Sawyer provides more of a general history and not too great of detail. If you're looking for something more detailed on the topic, I would suggest Viking Road to Byzantium by Hilda Ellis Davidson and The Varangians of Byzantium by Sigfús Blöndal trans. Benedikt S. Benedikz. Both are detailed and may provide you the best information overall. Davidson's book may be a bit harder to get a hold of if you are looking for it on Amazon or something.