Mikefm, your instinct matches one source, but opinions are rather mixed:
'Some authorities regard both
littler and
more little as non-standard. The OED says of the word little: "
the adjective has no recognized mode of comparison. The difficulty is commonly evaded by resort to a synonym (as smaller, smallest); some writers have ventured to employ the unrecognized forms littler, littlest, which are otherwise confined to dialect or imitations of childish or illiterate speech." ' --
Wiktionary online.
However, Bryan Garner says:
'
littler; littlest. These forms--the comparative and superlative for little--are perfectly good, although some writers have gotten the odd idea that they're not.'
Based on many examples I've used over the years, I've come to trust Garner's command, data, and instincts about many issues of usage, over other references I have or am familiar with. If you don't have this reference, I can highly recommend it: "A Dictionary of Modern American Usage". I have the 1998 edition, but there have been several revisions.
American Heritage says,
lit·tle (lĭt'l)
littler or
less (lĕs) (especially for senses 2, 3, 4),
littlest or
least (lēst) (especially for senses 2, 3, 4)
1. small, or smaller in comparison. 2. short in extent or duration, brief:
little time. 3. Small in quantity or degree:
little money. 4. Unimportant; trivial; insignificant;
little trouble. {Five other definitions follow.} --American Heritage Dictionary, New College Dictionary
NOAD has a long section, starting with the adjective (
lit·tle |'litl| adj. ) and omits the comparative and superlative, which by the rules of this dictionary means the forms are regular. Following that, it lists the adverb, not duplicating the headword ('little') because it's the same, but adding the other forms, because they're irregular: adv. (
less |les|,
least |lēst| ) to a small extent:
he reminded me a little of my parents. --New Oxford American Dictionary, Oxford University Press, 2001.