Understanding Basic Irish Grammar Using Scribd
I always struggled with understanding Irish grammar until I came upon a site called Scribd (scribd.com) where you can read books online and view documents for free. Anyways some publisher uploaded one of their books called Irish Grammar Book here s the linkhttps://www.scribd.com/doc/221735005/Irish-Grammar-Book
If you are on desktop you will have to download it after a few pages but on iPhone you can read the whole thing
It gives a great, detailed explanation of Irish grammar
I like Stenson's two, published by Routledge. They're workbooks, so give you a chance to practice what you learned as well. I also the Christian Brothers', though the English version isn't nearly as detailed as the Irish. Online, just use Gramadach na Gaeilge - it's free.