I have a new player started and found a book called Lightning, which I assume is a spell. Why can't I use or equip it? Does my character first have to attain a level where that spell is offered as a skill?
Yes, with the remastered version you need to meet the character level requirements to read a spell book. In the original version you could read one as soon as you found it, if you wanted to.
ah i used to play the really old version of DD, without any new patches few years ago. it sometimes was kinda annoying but fun as well. =) good old times :p