There is a walking tour that sets off from the tourist office, by the town hall, at 10.30am every day (and 2pm in the summer) - £12 and very good for a potted history. As well as the Roman tours, depending what day you're there, there are Viking, medieval, Stuart, women, and Edwardian Lady history tours too.
If you happen to be visiting end of May/beginning of June, it's the Heritage Festival when there will be loads of activities on covering the history & heritage of Chester - https://www.chesterheritagefestival.co.uk/
Bookshops - second hand, we have Amblongus, Aldous, Bookingham Palace (featuring Vinyl Richie for records); new books, Books on the Walls & Waterstones, waiting for the new book shop & wine bar to open.
Rather than Gail's, Kookaburra is round the corner - tiny but amazing baking. It's really hard to choose somewhere to eat because there are so many good places - my favourite is Porta (tapas) but for casual, the market has seafood, Thai, Indian, vegan, cheese, pizza, pasta, burgers, sandwiches and a more traditional cafe to choose from. And the cheese board at Paysan wine bar is bloody amazing.
There are a few galleries on Watergate Street, and there's Pictura on Eastgate Row for creating something yourself.