Counts of copies of ancient manuscripts of books with a claim to canonicity in one or more traditions, taken together with other lines of evidence, are an index of the relative importance attached to said books.
Counts of copies of books discussed in Thinking about Canon in the caves of Qumran are as follows: Gen (15); Exod (17); Lev (13); Num (8); Deut (29); Josh (2); Judg (3); 1-2 Sam (4); 1-2 Kgs (3); Isa (21); Ezek (6); the Twelve (8); Ps (36); Prov (2); Job (4); Song of Solomon (4); Ruth (4); Lam (4); Qoh (3); Esther (0); Daniel (8); Ezra (1); Neh (0); 1-2 Chron (1); Tobit (4); ben Sira (2); Letter of Jeremiah (1); Psalm 151 (1); precursors of 1 Enoch (20, counting copies of the Book of Giants); Jubilees (15 or 16); precursors to the Testaments of the Twelve Patriarchs (7 or 8).
The books/traditions which appear in the most copies are the following: Psalms (36); Deuteronomy (29); Isaiah (21); Enoch (20), and Jubilees (15 or 16). That Jubilees in particular was accorded a high degree of authority by the Qumran sect is suggested by several indicia; the high number of extant copies is, taken with the others, one more. Psalms, Isaiah, and Deuteronomy (in that order) are, as is true at Qumran, the three most quoted books in the New Testament. It thus transpires that said books were top-tier in a cross-section of late Second Temple Judaism.
That Esther is missing is probably not a coincidence. The sect did not celebrate the holiday the book mandates. The holiday and the book that mandates it may not have gained general currency within Judaism until the first cent. ce. It received universal or near universal approbation later still.
Pre-Christian biblical papyri in Greek, including Qumran fragments, attest to the following books: Gen (1); Exod (1); Lev (2); Num (1); Deut (4); Epistle of Jeremiah (1); the Twelve Prophets (1). The pattern of attestation is a witness to the exceptional importance of the Pentateuch, and Deuteronomy in particular, in 1st to 2nd cent. bce Greek-speaking Judaism.
Christian biblical manuscripts of the 2nd to 3rd cent. ce attest to the following books: Gen (8); Exod (8); Lev (3); Num (1); Deut (2); Josh (1); Judg (1); 2 Chr (2); Esther (2); Job (1); Ps (18); Prov (2); Qoh (2); Wisdom of Solomon (1); Ben Sira (2); Isa (6); Jer (2); Ezek (2); Dan (2); the Twelve (2); Bel and Susannah (1); Tobit (2); 2 Maccabees (1). The importance attached to Psalms, Genesis, Exodus, and Isaiah by early Christians is reflected in the counts.
 Data from James C. Vanderkam, The Dead Sea Scrolls Today (Grand Rapids: Eerdmans, 1994) 29-42; 149-58.
 For further discussion, see Vanderkam, Dead Sea Scrolls, 153-55.
 The alignment of Qumran and NT data in this sense is well-known. Cf. Martin Abegg, Jr., Peter Flint, and Eugene Ulrich, The Dead Sea Scrolls Bible (New York: HarperCollins, 1999) xvii.
 Data from Johan Lust, “Septuagint and Canon,” in The Biblical Canons (ed. Jean-Marie Auwers and H. J. de Jonge; BETL 163. Leuven: Leuven University Press, 2003) 39-55; 42.
 Data from Larry W. Hurtado, The Earliest Christian Artifacts: Manuscripts and Christian Origins (Grand Rapids: Eerdmans, 2006) 19-20.