Jane Austen's Pride and Prejudice gives many ideas that can be useful in constructing an Alphabet Book. Below are examples for the letters U and X-Z. Some letters have more than one example because I was able to think of more than one. But that was obviously not the case with every letter.
U is for ultimately. Elizabeth ultimately fell in love with Mr. Darcy because he proved his worth and honor.
U is for unadvisedly. Mr. Collins demonstrated impropriety by unadvisedly introducing himself to Mr. Darcy at Netherfield ball.
X is for X-chromosome. Longbourn is entailed to Mr. Collins due to a plethora of X-chromosomes in the Bennet family.
Y is for yield. Mr. Darcy was forced to yield to Wickham in paying his debts to force him to marry Lydia in order to save Elizabeth's reputation.
Y is for youthfulness. Lydia sacrificed her youthfulness and beauty by eloping with Wickham.
Z is for zany. Mr. Collins can be easily characterized as zany, "a man who is a stupid, incompetent fool" (Crossword Clue Solver, Definition-Zany).
K- Kent (where Lizzy goes to in Volume ll chapter 5) or Kitty (Lizzy's sister) or Miss Mary KING ( who was courted by Mr Wickham for her fortune)
Y- Mrs. Younge, former governess to Georgiana Darcy
Hope this helps. :)