I agree, Estrogen Matters (book) by Bluming is great. Also the Dr Louise Newson podcast has several episodes on bc and HRT use, analysing all the data we have to date. Search back through previous episodes. You should know that it's a decision you should make, weighing up the pros and the cons and the evidence. Don't feel that you just can't even consider it. Although you may have to complete your treatment first, before going on it. (I think Newson Health ask you to have completed treatment X weeks or months before seeing them for HRT.)
By the way, even if you don't want to take systemic HRT, it is officially safe to keep taking vaginal HRT (Vagifem and Ovestin) and you probably should do that, just to prevent vaginal atrophy from developing without estrogen. (Easier to prevent than to treat.) This is totally safe for women with a history of bc - my mum had estrogen positive bc and didn't take any vaginal estrogen and now has a vaginal prolapse, probably made much more likely due to not using regular local estrogen up there. She went to her GP to be diagnosed with the prolapse and her GP gave her the Vagifem pessaries and said they are considered totally safe for women with estrogen positive bc.