Reddit mentions of Saxo Grammaticus: The History of the Danes, Books I-IX: I. English Text; II. Commentary (Bks.1-9)

And on vikings - primary sources though not all of battles - here’s a quick overview of sources https://www.vikingeskibsmuseet.dk/en/professions/education/viking-knowledge/archaeology-and-history/written-sources-for-the-viking-age/

They may be found around the web but here are links to a few to buy

I can recommend the
Icelandic sagas, personally I find them great fun lots of skull bashings - you may have to buy them.

at least some are here https://sagadb.org Or here https://archive.org/details/sagalibrarydonei01snoriala


Icelandic sagas
https://www.amazon.com/Sagas-Icelanders-Penguin-Classics-Deluxe/dp/0141000031/ref=mp_s_a_1_1?keywords=icelandic+saga&qid=1559118780&s=gateway&sr=8-1

Saxo gramattucus or Saco’s saga (13th century danish ‘history’ of kings
https://www.amazon.com/Saxo-Grammaticus-History-English-Commentary/dp/0859915026


Snorris saga
https://www.amazon.com/Sagas-Norse-Kings-Snorri-Sturluson/dp/8209101730 - not sure if there is a newer more comprehensive translation as I read in original language

and the Eddas

Younger Edda
https://www.amazon.com/Edda-Illustrated-Snorri-Sturluson-ebook/dp/B00NCCEJ6O/ref=mp_s_a_1_6?keywords=edda+saga&qid=1559118593&s=gateway&sr=8-6

Elder Edda
https://www.amazon.com/Elder-Edda-Viking-Penguin-Classics/dp/0140435859/ref=mp_s_a_1_11?keywords=edda+saga&qid=1559118649&s=gateway&sr=8-11


And on vikings - primary sources though not all of battles

I can recommend the
Icelandic sagas, personally I find them great fun lots of skull bashings - you may have to buy them.

at least some are here https://sagadb.org Or here https://archive.org/details/sagalibrarydonei01snoriala


Icelandic sagas
https://www.amazon.com/Sagas-Icelanders-Penguin-Classics-Deluxe/dp/0141000031/ref=mp_s_a_1_1?keywords=icelandic+saga&qid=1559118780&s=gateway&sr=8-1

Saxo gramattucus or Saco’s saga (13th century danish ‘history’ of kings
https://www.amazon.com/Saxo-Grammaticus-History-English-Commentary/dp/0859915026


Snorris saga
https://www.amazon.com/Sagas-Norse-Kings-Snorri-Sturluson/dp/8209101730 - not sure if there is a newer more comprehensive translation as I read in original language

and the Eddas

Younger Edda
https://www.amazon.com/Edda-Illustrated-Snorri-Sturluson-ebook/dp/B00NCCEJ6O/ref=mp_s_a_1_6?keywords=edda+saga&qid=1559118593&s=gateway&sr=8-6

Elder Edda
https://www.amazon.com/Elder-Edda-Viking-Penguin-Classics/dp/0140435859/ref=mp_s_a_1_11?keywords=edda+saga&qid=1559118649&s=gateway&sr=8-11

https://www.amazon.co.uk/Saxo-Grammaticus-History-English-Commentary/dp/0859915026/ref=sr_1_1?ie=UTF8&qid=1550733074&sr=8-1&keywords=saxo+grammaticus

The book covers Danish and Nordic history up to the reign of "Gorm the Old" (year 958).

It's filled with Viking sagas, Ragnar Lothbrok (especially his sons) and the slow build up of the Kingdom of Denmark (Gorm the Old was the first real King of Denmark, all previous are regarded as chieftains or petty kings). Gorms son Harald is widely accepted as the one who Christened Denmark, probably because his father (gorm) was lenient on Christians living in Denmark during his reign.