Source: The Bankrupt Bookseller (1947), p. 30
“He used to say that "no book was so bad but that some good might be got out of it."”
Letter 5, 10, referring to Pliny the Elder.
Letters, Book III
Original
Dicere etiam solebat nullum esse librum tam malum ut non aliqua parte prodesset..
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Pliny the Younger 50
Roman writer 61–113Related quotes

Speech made on Lou Gehrig Appreciation Day at Yankee at Yankee Stadium (July 4, 1939)

“Too bad you got so bogged down in books. You've got the spirit of a warrior.”
Source: The Golden Lily

Things like that.
Simon O'Hagan "Credo:Peter Blake", http://www.findarticles.com/p/articles/mi_qn4159/is_20051120/ai_n15851377 The Independent on Sunday, 2005-11-20. Accessed from findarticles.com, 2007-01-22
Life

“Bad books engender bad habits, but bad habits engender good books.”

“There is no book so bad," said the bachelor, "but something good may be found in it.”
Source: Don Quixote de la Mancha (1605–1615), Part II (1615), Book III, Ch. 3.

Quoted in "Tony Abbott under fire" http://www.abc.net.au/am/stories/s596135.htm on abc.net.au, July 22, 2002.
2002

On reading books that might be deemed inappropriate in “We Read To Challenge Ourselves: An Interview With Mariko Tamaki” https://comicsalliance.com/mariko-tamaki-pride-week-interview/ in Comics Alliance (2016 Jun 24)