@
jerbes - if you have a lot of books like this then you could make use of the
API for the function mode search and replace to take care of all the unambiguous contractions (eg theyre, Im etc). That will avoid inadvertent placement of misspelt contractions into a user dictionary - I've done it myself so I know it's easy to do.
But neither it nor the spell checker will help with -- its/it's, well/we'll, cant/can't, wont/won't etc. You need to search for those, read the sentence, and adjust as necessary.
BR