Having known about the forgeries from the beginning it was interesting to see how Ackroyd worked up to the big reveal. Less satisfying were the strange ways he changed things around, making Edmond Malone a defender of Ireland's "discoveries" instead of the scholar who debunked them. Little things like that, as well as changing dates around (having Mary die in 1804 instead of 1847, and making her, Charles and Ireland seem much closer in age than they were).
For all my quibbles with the way he did it, I loved the book. Charles and Mary's senile father with his random jabberings provided some excellent comic relief, and Samuel Ireland (William's Shakespeare-obsessed and ever-gullible father) were really good characters, and watching William Henry Ireland himself go through the process of disguising, dissembling and eventually confessing his actions made for fascinating reading. I think I might finally pull his Confessions off the shelf now.