Translation:In October we read less often than in July.
other way actually, in October you have school and in July there's summer vacation...
"We read more seldom in october than in july"
Is this really wrong? The answer provided seemed more or less synonymous to my suggestion. I suppose "seldomly" seems more "adverb-y" but I really don't think it's called that. Is there some other reason this could be deemed wrong?
Technically you are right I suppose, although I think that using a comparative with "seldom" is highly unlikely.
"less often" = "rzadziej" (e.g. only once a week instead of daily), "less" = "mniej" (e.g. only one book in month instead of four books - you could still read often, but in total you read less (for example, because you read daily, but only for five minutes))