John Narvesen/ Aslaug Olsdatter

I found a site on My Heritage that has info on my gg grandfather John Narvesen b. Dec. 28 1815 from Sandsvaer, Buskerud, Norway. He was Married to Aslaug Olsdatter b. Oct 15 1826. The site is Sandsvaer Familys The info comes from a Bygdebook, on the My Heritage site. I had most of the info on his site from what family had researched before and what i could figure out from Census and Parish Data. I had never heard of Bydebooks before and wonder what is actually says. Also I have Narves parents listed as Narve Truelsen b. abt 1775 Baptized April 8 1775. His mother as Rønnoug Olsdatter. the 1801 Census if its the same person has her listed as Rønnev Anbiørnsdatter. I would like to find more about them their marriage date and children. Aslaug parents I have as Ole Ingebretson b. abt.1795 and Marthe Arnesdatter b.abt 1791 think they might be from Kongsberg. Aslaug and most of their children Immigrated to the United States My g grandfather was Tinius Johnson b. Jan.15 1864 he Immigrated in 1882 first to Massachusetts then New Sweden Aroostook county Maine, USA. If anyone wants info on the other Children of John and Aslaug. I can help. Would love help with the older generation since I cant read Norwegian. Thanks Kim