when my mental health was at its lowest i found it really difficult to focus on reading but still really wanted to. My solution was audiobooks and at first it was hard to get into them but the more I did, the easier it got. It takes away some mental strain of reading too like trying to read it in the right tone or imagining their voices.
Some recs: the girl on the train (keeps you on your toes), the martian (funny, helped my mental health), throne of glass (adventure and whole new world), an inspector calls (is a play but is just so good), the love hypothesis (cutesy, quick easy read)
you could also read textbooks! Learning something new :)