chess books on the Scandinavian with 2.Nf6?
I second Novacek's suggestion. If you are after the gambit lines then Smerdon's Scandinavian is the best choice as its a fun book to read and he is one of the few top players to have played it regularly.
Other book worth noting is a black repertoire book by Vincent Moret. He uses the Portuguese & Icelandic repertoire vs e4 and against d4 suggests stonewall and Albin counter gambit. He uses some lines from Smerdon' book.
Older books are one by Selby Anderson on the Portuguese Gambit and an opening repertoire book by Keene and Levy which are both really old.
... Smerdon's Scandinavian …
http://www.jeremysilman.com/shop/pc/Smerdons-Scandinavian-76p3919.htm
... a black repertoire book by Jean Moret. ...
https://www.newinchess.com/media/wysiwyg/product_pdf/9050.pdf
https://chessbookreviews.wordpress.com/tag/vincent-moret/