I see that there were many booksellers in Victorian London. Was there a particular area that hosted "respectable bookshops", in the manner that Petticoat Lane was a centre for Victorian clothing?
This page on London during the Victorian era offers (emphasis mine):
Further, there are the streets and districts for particular trades, as Long Acre, where the carriage-makers abound; and Lombard Street, where the bankers love to congregate; and Clerkenwell, the district for the watch-makers; and Hatton Garden for the Italian glass-blowers; and the Borough for the hatters; Bermondsey for the tanners; Lambeth for the potters; and Spitalflelds for weavers; and Catherine Street for the newsvendors; and Paternoster Row for the booksellers; and the New Road for the zinc-workers: and Lower Thames Street for the merchants in oranges and foreign fruits; and Mincing Lane for the wholesale grocers; and Holywell Street and Rosemary Lane for old clothes; and so on.
The footnote suggests it's a quote from a book named "The Great World of the London Streets" by Henry Mayhew, 1862. Googling yields a very similarly titled book, "The Great World of London" by the same author from around the same time (1856) that apparently ended up published under a slightly different title in 1862. The online book contains the above quote.
(The quote doesn't say it was a street where "respectable" bookshops were concentrated.)
Editing to add, courtesy of Steve Bird, that the wikipedia article on Paternoster Row also offers that:
In 1819 Paternoster Row was described as "almost synonymous" with the book trade.
Based on: A Pictorial and Descriptive Guide to London and Its Environs: With Two Large Section Plans of Central London... Ward, Lock & Company, Limited. 1819.