The magazine was Raph Ginzburg’s third attempt at a subscription title, first was the erotic Eros 1962, fact 1964 and Avant Garde 1968 (followed by the newspaper Moneysworth) and I have a prototype of Avant Garde fortnightly newspaper from 1974. They all failed, primarily I think, because of a lack of advertising to help cover the costs. The secondary problem was that the editorial in all of these titles really wasn’t strong enough to sustain long term readership interest even though they had relatively low subscription costs.
My interest in the publications is because they were all designed by Herb Lubalin. He excelled with the four quarterly issues of Eros (I uploaded the first issue in August 2011 and issue two in March 2012) fact was a problem because of a very inflexible two column format no color and cheap paper. Avant Garde fortunately was a large square (about eleven inches) magazine with some four color on a semi-matt gloss though the rest of the paper was a nothing special bond. It started off as a bimonthly and ended as a quarterly in 1971 with issue fourteen. The last issue had eleven pages of ads, five of them were for Ginzburg products.
Check out the title with Wikipedia for some background detail. Elsewhere the magazine is usually mentioned in design books because of the Avant Garde typeface used on the cover.