Implied Readership: Both higher class and lower class people at different times. Not much else can be seen. The early price for this magazine ($1.50 for a subscription, 15 cents for a copy) shows that this magazine is attempting to reach a wider, lower-class audience. The price raising over time, the print quality getting higher, and the ads which are mostly for articles and books (and the occasional magazine), show that the magazine is trying to target people who are on the higher end of the spectrum.
Circulation: No explicit data about circulation could be found, though the content was very polarizing so this probably wasn't the most popular magazine.
Regular Contributors: James Joyce is probably the most famous contributor. He published Ulysses in The Little Review, and the 'explicit' content resulted in a lawsuit against the magazine. Other contributors include Djuna Barnes, T. S. Eliot, Wyndham Lewis, Mina Loy, Francis Picabia, Dorothy Richardson, May Sinclair, Gertrude Stein, W. C. Williams, and W. B. Yeats. Ezra Pound and Jane Heap don't contribute any content, but they do become co-editors.
Contents: The content (the "obscene" Ulysses, and the partially blank September 1916) shows that it's attempting to reach an audience that is looking for more experimental works. Editions frequently feature anarchism and feminism. Literature shown is often highly plotically contriversal, and styles and subjects are experimental.
Editor: Margaret Anderson is the only editor ever listed. She's a publicly expressive anarchist and feminist. She was probably a very polarizing presence. She's uncompromising (or wants to appear that way), and if something isn't up to her standards she won't show it.
Format: Images seem to be shown more and more over the years, but the meat of the magazine is literature. Both poetry and articles are featured frequently. Magazine seems inconsistent on format. One issue might be in the mid thirties for number of pages, and the issue after might be brushing seventy.
History: Magazine began 1914 and ended 1922. This magazine saw the start of World War 1, and showed the effects of that. Many early editions are heavy on anarchistic themes, and one edition held an apology from the editor for having to raise the prices of subscriptions due to the war.
Putting it all together: A very polarizing magazine. Often having strong magazine with strong political undertones and extremely experimental or shocking content, this was a magazine that the general public probably didn't have the best opinion of. It's influence is undeniable, however. Managing to get a lawsuit against it, it spread its influence far, even if people didn't like it.
Sources:
The Modernist Journals Project (searchable database). Brown and Tulsa Universities, ongoing. www.modjourn.or
Anderson, Margaret. The Little Review.
La Casse, Christopher J. "“Scrappy and Unselective”: Rising Wartime Paper Costs and the Little Review." American Periodicals: A Journal of History & Criticism, vol. 26 no. 2, 2016, p. 208-221. Project MUSE muse.jhu.edu/article/628768.
Keenan, Owen. "Margaret C. Anderson." Legacy Project Chicago. https://legacyprojectchicago.org/person/margaret-c-anderson. Accessed 9, Sept. 2021.