THEY'RE OFFERING art-to-go at the Corcoran, and it's a bargain. An exhibition of 70 etchings by James McNeill Whistler and two of his contemporaries is accompanied by a take-home portfolio of 18 prints for only $14.95.

Drawn from the Corcoran's vast collection of works on paper, the exhibit explores the artistic and emotional dynamics among Whistler (1834-1903); Francis Seymour Haden (1818-1910), his English rival; and Joseph Pennell (1857- 1926), Whistler's American disciple.

Haden, a prominent London surgeon and noted artist, was Whistler's brother-in-law and, for some years, his friend and self-assigned mentor. Although clearly the lesser talent -- Whistler could suggest with one stroke a finer human figure than anatomist Haden ever executed -- Haden was more highly regarded than Whistler in his lifetime, and never let the younger man forget it.

Pennell modeled his etching technique on Whistler's, became his biographer, and spent much of his life in Europe largely because of Whistler's presence there. Pennell produced his finest and most original work only after his hero died.

The portfolio's scholarly comments by Linda Crocker Simmons and Emily J. Nash are pointed and informative without pretending omniscience. They include some vivid vignettes: The final break between Haden and Whistler came when Haden casually ordered the burial of James Reeves Traer, Whistler's friend and physician (who had died suddenly in a Paris brothel), without even informing the man's family or friends that he was dead. Whistler found Haden in a Paris cafe, and there followed a punch-up that ended with Whistler throwing Haden through a plate-glass window.

The etchings are shrewdly selected, are nicely printed on heavy, handsome stock and are held unbound in the antique-style portfolio, which also contains a concise historical essay, a detailed chronology of the overlapping of the three artist's lives and an exhibition checklist.

HADEN, WHISTLER, PENNELL: Three Master Printmakers -- Through Dec. 2 at the Corcoran Gallery of Art, 17th Street and New York Avenue NW. 638-3211. Open 10 to 4:30 Tuesday through Sunday and 10 to 9 on Thursdays. Metro: Farragut West. Call ahead for wheelchair access.