The Duchess of Bloomsbury Street

Incisive description of people, romantic description of places encountered, hilarious description of events that took place. Absolutely charming follow up to 84, Charing Cross Road; though I read them out of order, I feel like in combination with ‘Q's Legacy', I've completed a memoir/epistolary trilogy. 
Hanff also has two books about living in New York that, after seeing how competent she is at non fiction, I'm now eager to read. 
Agree with Sykes' introduction: you will enjoy this more if you've read 84, Charing Cross Road first. Though, don't recommend reading the introduction in this edition before the book, as it does what so many introductions insist on doing, telling you about passages from the book you're about to read. Which is why I stick to my policy of reading introductions after I've finished the book.