The journalists Jake Tapper of CNN and Alex Thompson of Axios have written a book named "Original Sin." They are discussing and describing in this book how Joe Biden's advisors tried to ignore or cover up Biden's physical and mental decline.
The book does not contain anything astonishing that changes broad reception, but is more anecdotical. Also most sources are kept anonymous, because they still do fear it seems the long arm of the Dems.
During his 2020 campaign Biden repeatedly forgot and confused names of people he had known for years, like Mike Donilon who as aide worked for him since the 1980s, George Clooney (who was so shocked about it that he later wrote an essay in NYT asking Biden to drop out), Xavier Becerra and so on. People described him as fragile and worried he might need a wheelchair in his second term. Also cabinet gatherings were mostly scripted. Mike Quigley, a Democrat from Illinois, described Biden's physical abilities on his trip to Ireland similar to his own father who was dying of Parkisons's disease.
So far Biden's team has not made any comment upon it, they are going to review it once it comes out.