IN SEARCH OF SHAKESPEARE; A Reconnaissance into The Poet's Life and Handwriting. By Charles Hamilton. Harcourt Brace Jovanovich. 271 pp. $34.95; SHAKESPEARE AND OTHERS. By S. Schoenbaum. Folger Books/The Folger Shakespeare Library. 285 pp. $28.50.

IT HAS LONG BEEN a source of wonder that the most expressive writer in English should have left us only six meager samples of his handwriting, viz., the elegant subscription "By me William Shakespeare" on the last page of his will, and five other crabbed signatures on various legal documents. To this pitiful hoard, according to Charles Hamilton -- an experienced authenticator of autographs, whose expertise helped to expose the recent "Hitler diaries" as fake -- we must now add 10 or more sheets of writing and drawings. He believes the following items to be in Shakespeare's own true hand:

1) All three pages of the Stratford will, including the Latin introduction. 2) Three early applications to the College of Heralds for a coat of arms (two in 1596, one in 1599). 3) Various sketches of coats of arms in the margins of these applications. 4) and 5) The Quiney-Mountford deed of 1612, and the Welcombe Enclosure agreement of 1614 (our poet apparently did not mind serving as a legal amanuensis). 6) The three pages of The Booke of Thomas More, which others have also claimed as Shakespeare's. 7) The pen-and-ink drawing of seven actors in Titus Andronicus, in which Hamilton believes one kneeling figure is a self-portrait of Shakespeare as an actor in costume. 8) Some pages of the "Northumberland Manuscript," which prove (this is a switch!) that Francis Bacon hired Shakespeare to edit and rewrite his essays.

Can all this be deduced from six signatures? To allay one's overstrained credulity, Hamilton uses a large format with numerous examples of Elizabethan hands -- secretary, cursive, and italic. Experts, he says, rely on the "feel" of an individual's handwriting. Does this make handwriting analysis a science? I recall the experience of my friend and publishing colleague Beverly Loo, who was Clifford Irving's editor. When he handed her the holograph manuscript of Howard Hughes' "autobiography," she took the wise precaution of soliciting expert opinions in advance, and they confirmed its authenticity so conclusively that it became a Book of the Month. At the same time it was signed up by an English publisher who assured me, with the certainty of a man who had served in wartime British intelligence, that it was indeed the work of the reclusive financier -- except that just before publication Hughes himself blew the whistle.

In his book Hamilton presents page after page of plausible evidence. To the inexpert eye the scribbling in the supposed Shakespeare documents appears to be similar. But isn't it possible that the scriveners, the Bartlebys of their day, were all taught the same penmanship, just as my generation was taught the Palmer method? And even if it were true that Shakespeare had legal training, knew heraldry, and liked to draw, would he, a hard-working playwright, have taken the time to pen these deadly dull legal words when he had a lawyer, Francis Collins, who could delegate such tedious chores to scriveners? Hamilton proves that Collins, as well as Sir William Dethick of the College of Heralds, could not have written documents attributed to them, but this does not prove Shakespeare was the writer.

The speculation that Shakespeare may have been murdered by his son-in-law Thomas Quiney (who feared that Judith Shakespeare was about to be disowned in her father's will) is the most sensational item in Hamilton's book. He not only detects signs of failing health (from arsenic poisoning) within the will, but cites the following as proof of Shakespeare's mental confusion: "He writes 'my neece eth Hall' in alluding to his beloved little granddaughter. . . This apparent blunder foretells the cerebral collapse that will overtake him in a few minutes." The Oxford English Dictionary's first definition of ''niece" could have saved Hamilton from making a blunder of his own: "Niece. A grand- daughter . . . (common till 17th cent.)" Though I would like to think tht at least some of Hamilton's eight samples are Shakespeare's, I remain skeptical.

SAMUEL SCHOENBAUM's Shakespeare and Others is a collection of essays, lectures and reviews over 25 years. At one point the author, a disciple of the great Alfred Harbage, modestly refers to himself as a "journal-wearied professional Shakespearean," which has not prevented him from writing with grace, wit and common sense. My favorite is his series of essays on the Dark Lady of the sonnets, which show that the egregious Dr. A.L. Rowse committed a pair of scholarly blunders when identifying Emilia Bassano Lanier as our poet's mistress: "Rowse is wrong about the name of the lady's husband; she married Alfonse, not William, Lanier. . . (The) odd phrase, 'very brown in youth' . . . is not brown at all, but brave." It is amusing to know Dr. Rowse never admitted these errors, unless correcting them later without comment constitutes an admission.

The essays on Ben Jonson's art and on the problem of his ambivalent attitude to Shakespeare are fascinating. Jonson's carping criticism of Julius Caesar, a play whose success must have rankled with Ben, shows that he was only human. "Oh how the audience were ravished" by Julius Caesar, wrote Leonard Digges, a contemporary of both poets whom Schoenbaum curiously fails to cite, and Digges' adjective for Sejanus, Jonson's Roman play, was "irksome." All this is outweighed by Jonson's high praise of Shakepeare in his First Folio poem, and by his testimony that "I loved the man, this side idolatry."

There are essays on Shakespeare's keen sense of political realism in Richard II; an unpublished contemporary account of William Henry Ireland's forgeries; the late E. Tangye Lean's researches into Elizabethan Stratford; the Folger Library's 50th anniversary in 1982, and much more. Schoenbaum's article of faith that "scholarship and criticism should be fun for the practitioner" is amply demonstrated in Shakespeare and Others.