Generally speaking, you might want to reference Peter Sawyer's Oxford Illustrated History of the Vikings (2001) to get a feel for the timeline of events and Brink and Price's Viking World (2008) for background on basic issues and themes like society, urbanism, and economics. Speaking more specifically to the North Sea, there's a wealth of resources out there, and I'd point especially to Barrett's Contact, Continuity, and Collapse: The Norse Colonization of the North Atlantic (2003), Forte et al's Viking Empires (2005), Hadley's Vikings in England (2006), Bately and Englert's Ohthere’s Voyages (2007), Barrett and Gibbon's Maritime Societies of the Viking and Medieval World (2015). Regarding the Netherlands , check out Simek and Engel's Vikings on the Rhine (2004). A quick check of my own library holdings turned up two additional volumes which might certainly be of interest—Bolton et al's Celtic-Norse Relationships in the Irish Sea (2014) and Hines and IJssennagger's Frisians and their North Sea Neighbours (2017)—but I haven't had the chance to look through these yet. There's a fair amount out there, and once you identify a few scholars focused on your interest area, I'd recommend searching for other books or articles they've written or other edited volumes that they appear in. I hope that gets you started!