Hey! Thanks for playing it, and all the way through even! :)
Yes, definitely. A save/load/overwrite confirmation would be a nice addition. Regarding buying spells before you have a spellbook. Others have mentioned this too, so I guess what I should've done is not allow the player to buy spells until he/she found the spellbook. Instead have the shopkeeper say "But sir, where will you put that spell? You don't have a spellbook!".
I'm happy you liked it :)