The book is definitely NOT meant for first time Alice readers. You need to be very familiar with the contents to get the most out of the fantastic information added throughout, but for afficionados it is a must read.
It contains suggestions for the original of every parody Carroll wrote. My favourite is this one, offered as the original of Humpty Dumpty's song that isn't sung;
In summer when the days were long
We walked, two friends in field and wood
Our heart was light, our step was strong
And life lay round us fair and good.
It's by a poet called Wathen Mark Wilks Call but is apparently most often anonymised in Victorian anthologies.
How deeply you delve into each footnote is going be a reflection both of your own interests and, if I'm honest, your stamina. I admit the scientific and philosophical references were generally too much for me, and the details of the chess game played out as Alice journeys from pawn to Queen in Looking Glass world I could only make the most perfunctory sense of, but I am sure they will be riveting to some readers.
On the other hand, I adored the fact that Carroll's diary entry for 9/12/1888 reads
' Concocted a new Proportional Representation scheme - far the best I have yet devised
- we need it NOW!!
And this: aged 13 (yes 13) Carroll wrote a parody of a passage from Henry IV part II. Prefiguring Humpty Dumpty's declaration that a word means just what he wants it to mean, as well as the nonsense of Jabberwocky, Carroll has the Prince introduce the word 'rigol' into his conversation with the King.
What meaneth rigol? asks the King
My liege I know not save that it doth enter most apt into the metre.
True, it doth, but wherefore use a word which hath no meaning?
My lord, the word is said, for it hath passed my lips and all the powers on earth cannot unsay it.
The book concludes with an episode called A Wasp in a Wig, which Carroll left out of Looking Glass partly at the suggestion of John Tenniel, whose original illustrations are included in the book and are also fairly extensively annotated. While not the strongest example of Carroll's inventiveness, this episode is closely referenced by Martin Gardner as showing Alice's character in a particularly kind and gentle light.
And this leads me to conclude with the observation that Gardner deliberately chooses NOT to include psychoanalytical references to Carroll and that he very firmly takes the view that Lewis Carroll's well known love for his 'child friends' (only girls, he didn't like little boys at all!) was entirely chaste. You have to make up your own mind, I'm still not really sure, but I love his books.