The first 10 Modern Library Paperbacks were reprints from the regular series.  Many more reprints were planned, but after the first 10 the titles were mostly new.  Of the next 57 titles, how many ML paperbacks were also regular (or giant) series titles, and which were they?  Which 2 were in print at the same time as the regular title?

Answer:

The following 10 paperbacks were also ML regular (or giant) titles (although introductions may be different):

P16 Of Human Bondage (176)
P20 The Sea and the Jungle (99.1)
P21 Famous Ghost Stories (73.1)
P23 Against the Grain (183.1)
P25 Troilus and Cressida (126.2)
P32 BUtterfield 8 (323.1)
P33 The Captain’s Daughter and Other Great Stories (Overlap with G62.1)
P40 The Seven that were Hanged  (Superset of 45.1)
P42 3 Lives (211.1)
P54 The Apocrypha (326.1)

Both P16 and P21 were in print at the same time as the regular title.  While P16 had an introduction added, P21 was identical to the regular title.