John Barth:
Main Themes & Characters
main characters
Early they are enamored of the world, happy, carefree, curious [e.g. Todd, Eben, the sperm]

But then something horrid destroys their joyful innocence--they let their curiosity get the better of them, they start thinking about things too much, and before long they are mixed up in such dizzying complexity that they come near to falling into what ...Ebenezer Cooke calls the pit.

Todd--broods about his heart disease until he decides to kill himself.

Jake--about the lack of reasons for action--paralyzed

Eben--about the too-many reasons for action--paralyzed

Giles--about the meaning of life until he twice destroys the university with his counsel, is constricted by paradox and his mind almost cracked

the sperm--about the meaning of his journey  (Morrell 101-)

main characters' dilemma Barth summed up his protagonists' dilemma this way: An imaginative enough temperament, given a liberal enough education, may find itself bound between two great premises of Western civilization: the lesson of Socrates, that the unexamined life isn't worth living, and the lesson of King Oedipus, that the well-examined life may turn out to be unlivable. (Morrell 102-03)
main characters' masks/roles
So when B's protagonists examine their lives and their world until everything becomes intolerably complex and overpowering, they escape by shifting their characters and distorting their situation, by putting on masks to face what they are up against.
e.g. Todd-- a rake, saint, cynic, and relativist.
Horner--a nihilist, an "owl, peacock, chameleon, donkey, and popinjay"
Eben--a gentleman, poet, and virgin
Giles--a student, hero, and Grand Tutor

The trouble is that the protagonists are not always able to come up with viable roles to play...--crisis

(Morrell 103-04)
main characters' crisis (1) [Todd's] main crisis occurs when the mask of cynicism no longer hides his mind from his heart, and he is never all right again until he assumes the new mask of relativist.

Horner--keeps in motion by practicing a variety of roles...then he nearly immobilizes himself because, as the Doctor points out, he gives himself the "wrong part" to play, that of penitent instead of villain....[his new role] autobiographer.

Eben--adheres too much to his role of moral innocent, and the crisis comes when he realizes how much harm he has done himself and others by persisting in that role.---the role of penitent. 

(Morrell 104-05)
main characters' crisis (2) Giles--finds himself to be the wrong kind of Tutor.

Storytells in LF--the crisis in their lives a continuing one--what and how to keep writing--since to stop would mean getting lost, pining away, or killing themselves in the funhouse of the world.

(Morrell 104-05)
(v.s. cosmopsis)
Each book brings its hero in contact with a mythotherapist par excellence: Captain Adam, the Doctor, Henry Burlingame, Harold Bray, Proteus, each so equipped with multi-personalities that none is ever caught with a mask down. They are what H. Burlingame describes himself: Cosmopholites, Creation, Cosmic Lovers...

Their Cosmophilism is at one end of a spectrum, the opposite of which is Cosmopsis; both are based on a knowledge of the world's complexity, but mobility is the nature of the first and paralysis of the second...In between, each protagonist vacillates, now paralyzed, now relatively fluid.

(Morrell 106)
mythopoeic vision(1)  The central idea of the mythic, as Joseph Campbell and others have demonstrated, is cosmic harmony, unity in multeity, and this idea recurs implicitly or explicitly in each book.

Barth's first two protagonists, terrified by the unity they glimpse, retreat behind a shield of words.

SW--Henry Burlingame deliberately seeks cosmic harmony,

GGB--George, transcending categories, achieves it.

The problem of the mythopoeic writer is how to translate mythic intimations, which are finally ineffable, into words capable of evoking that which may not be articulated. Barth's next two books, LF and Ch, address this difficulty, the former focusing primarily on the relationship between sex, language, and myth; the latter, by far the most "socially conscious" of Barth's first six books, showing how myth may inform life as well as art.
(Harris 7)

  Letters, ..., completes this return to the world while affirming that it is a worded world after all. Language, properly employed, is the mythic though perhaps not mysitc ligature connecting man, time, and world in a dynamic unity.
(Harris 7)