Joshua burned Ai may be a summary to the narrative and not an additional action on the part of Joshua (see verse 19). This may also be translated as either “Joshua caused the city of Ai to be burned” or “Joshua and his men burned the city of Ai.” The translation should not leave the impression that Joshua alone burned the city.

The city was left … in ruins, a condition which persisted to the time the account was written (today). It is important that the reader not confuse today, the time of the writing of the book, with “today,” the time of the reading of the book. To avoid this possibility of misunderstanding, one may translate “The city is still in ruins today, as I write this story to tell you about it.” If this restructuring is followed, it is obvious that the word chosen for “story” should suggest a “true story” as opposed to an invented story.

Quoted with permission from Bratcher, Robert G. and Newman, Barclay M. A Handbook on Joshua. (UBS Helps for Translators). New York: UBS, 1983. For this and other handbooks for translators see here .