I noticed that the book of Esther uses, often very awkwardly, the present tense to describe things that usually are written in the past tense (I didn't notice this much use of the present tense in other biblical books).
Here are some examples:
1:1: הַמֹּלֵךְ (who is ruling): It should have just said אשר מלך, or שמלך. Rashi says that it means that he ruled because of himself, and he wasn't from the royal line, so this one isn't really a problem, but I included it to show the pattern.
2:11: מָרְדֳּכַי מִתְהַלֵּךְ (Mordechai is walking): It should have said התהלך.
2:19: וּמָרְדֳּכַי יֹשֵׁב (and Mordechai is sitting): It should have said יָשַב.
2:20: אֵין אֶסְתֵּר מַגֶּדֶת (Ester is not telling): It should have said אסתר לא הגידה.
Ibid.: אֶסְתֵּר עֹשָׂה (Ester is doing): It should have said עשתה.
3:2: כֹּרְעִים וּמִשְׁתַּחֲוִים (are kneeling and bowing): It should have said כרעו והשתחוו.
7:8: וְהָמָן נֹפֵל (and Haman is falling) It should have said נפל.
9:4: וְשָׁמְעוֹ הוֹלֵךְ (and hearing of him is going): It should have said הלך.
9:21: לִהְיוֹת עֹשִׂים (to be doing): It should have said לעשות.
These tenses are so important that if one changed present to past he doesn't fulfill his obligation even bedi'avad (Mishnah Brurah 690:51)!
What is the reason for so much use of the present tense?
(Conversely, there was one past tense that I thought should be present (6:8): וְסוּס אֲשֶׁר רָכַב עָלָיו הַמֶּלֶךְ (a horse on which the king rode): Shouldn't it be on which the king rides (consistently)? What does it matter if the king rode on it once?)