Genius Bonus: And just in case you couldn't understand the reference, Niffenegger is happy to spend a few paragraphs explaining.
Padding: The middle third of the book goes into a lot of detail about (1) Henry and Clare's sex life, and (2) Clare's family. You could skip 100 pages in the middle and lose very little in terms of actual plot.
There's also the equally 'wonderful' fact that Henry is forty when he and Clare have sex for... well, first time for Clare... their first time... Anyway, Clare is eighteen.
He just happened to appear to her on the night of her 18th birthday. And at least she was legal.
In fairness to Henry, Clare had spent the past two years of her life actively trying to get Henry to take her virginity, to the point of hiding the clothes he wore while in her past.
This is noted as a major problem of the film. The book can kind of get away with a naked adult man talking to his future wife as a young girl, but when you actually have to see it, the ickiness is unavoidable.
Clare. Let's look at her life in detail, shall we? VERY dysfunctional family and childhood, at one point finding her mother after her suicide attempt. Having an unusual and confusing relationship with a man who is very rarely ever there. Teased all through her adolescence for never dating. The one time she DOES try to date someone, she ends up BEATEN, BURNED, and physically and emotionally scarred. She has around twenty years of wedded bliss with Henry—which is STILL intercut with his constant comings and goings, and the repercussions of said comings and goings, the miscarriages (at more than one point finding the fetuses outside her body), her wacky homelife and the death of her mother. And then, she has to deal with her husband dying in her arms and living a life of single motherhood, never getting into another relationship again. Ow.
So she spends about three-quarters of her life alone. Ow indeed.
Ingrid. Paired with Fridge Logic (if not Fridge Horror): why doesn't she get over Henry and always desperately hoped to marry him? It is revealed that Alba time-traveled to them when they still were a couple. While Henry in his twenties is totally oblivious who that weird, bare-footed kid who follows him around is, Ingrid is implied to figure it out. She must assume Alba is her and Henry's daughter in the future.