long enough

Paradise Lost is one of the books which the reader admires and puts down, and forgets to take up again. None ever wished it longer than it is. Its perusal is a duty rather than pleasure.

—Samuel Johnson, “Milton,” The Lives of the English Poets

can't take out anything

Disce quod ignoras: Marsi doctique Pedonis
saepe duplex unum pagina tractat opus.
Non sunt longa quibus nihil est quod demere possis,
sed tu, Cosconi, disticha longa facis.

Learn what you don't know: one work of (Domitius) Marsus or
    learned Pedo
often stretches out over a doublesided page.
A work isn't long if you can't take anything out of it,
but you, Cosconius, write even a couplet too long.

—Martial

multum in parvo

The phrase multum in parvo has always had a special significance for me. In its terse and compact Latin diction, it exemplifies exactly what it connotes: much in little. The archetype of brevity, however, is not easy to define. Abstraction, conciseness, symbolism, and imaginative potential are basic in the concept. A multiplicity of detail is concentrated into a unified principle, the particular is transformed into the universal, a largeness of meaning is conveyed with the utmost economy of means. This largeness of meaning should be accomplished by a dramatic impact, in a word: insight with a gasp.

—Carl Zigrosser, Multum In Parvo (George Braziller, 1965)