Poor Nell!! I guess she never really found out who she was. I didn't see the twist with Eliza and Nathaniel coming. I had weird Uncle Linus pegged as the father because of what William Martin told Nell. That was a great red herring!!
And don't you just feel terrible for Eliza at the end. Adeline is one of the most hateful characters I've ever read. rose comes a close second place  

I liked the sort of hidden garden idea which seems to have come from the Secret Garden. In fact one particular bit seems to have been just lifted out of the SG. The bit where the cousins meet and Eliza throws open the windows of Rose's (the invalid's) room is exactly what Mary Lennox does when she meets Colin. I suppose that's why she had Frances Hodgson Burnett (who wasn't an American by birth btw she was born in Manchester) make a brief, rather odd appearence.

I did enjoy it and it kept me guessing, not quite to the end but far enough. I like the shifts in time. I agree nic Adeline was a horrible woman! and so was Rose come to think of it and Linus was a strange invention because he was creepy but he seemed to be a red herring.

I guessed quite early who was Nell's parents and didn't believe it was Mary even though we were led in that direction.  But I did at one time have my doubts about Nathaniel being her Dad and thought Linus must have raped Eliza, he was really very odd. The way the book was written going back and forth in time kept you reading.  One chapter would end on a cliff hanger then you had to read some more chapters to get back to what happened next.  At one time I thought the story was going to go back to the beginning of time when it went back to Linus and Adeline's childhood but fortunately the family history stopped there.  I was worried the story would be overloaded with characters if the story went back to far.  Was it believable?  Yes in the main I think it was for the type of book it was.  I felt sorry for Nell.  What was her Australian Dad thinking of  to tell her she had been a foundling on her birthday!  
I am quite interested in Family History and like to look in to my own family, but you do wonder sometimes if the people really are who it says there are.  I bet there are many families whose birth certificates don't tell the whole truth.  I can quite believe that the importance of carrying on the family line made some families resort to all sorts to achieve this aim.  Thought Nathaniel was a wimp of a man though, being totally ruled by his mother in law.  Mine you he did get to sleep with the attractive Eliza with hie wife and mother in laws blessing.  It was a shame Eliza got pregnant so quick as I'm sure he wouldn't have complained about having to try again. It was sad that Rose had been experimented on with the x ray to find the thimble.  I was puzzled as to why that episode was in the book, not realising the significance until later.
The inclusion of Linus was a bit odd.  He seemed to be a minor character that poped up occasionally but did play an important part in the story.  By having Georgina's husband killed he sealed the fate of Eliza.

I did guess that Eliza was Nell's mother, but couldn't work out how that could be, so I kept going back to the expected Rose and Nathaniel parentage. I didn't expect it to work out the way it did.

I agree that the Uncle Linus character was an odd one, and I did keep expecting a rape / incest scene at some point. Although I was very glad when that didn't happen.

Poor Eliza and Nell, what tragedies for them both for differing reasons.