The verb lesen is irregular in the present tense. Like many other irregular verbs, it changes the stem vowel in the second and third person singular forms (du and er/sie/es).
lesen to read
ich lese
wir lesen
du liest
ihr lest
er/sie/es liest
sie lesen
der alte König
Was liest du, Froschkönig?
What are you reading, Frog King?
der Froschkönig
Ich lese einen Roman. Er geht um einen verzauberten Prinzen ...
I am reading a novel. It's about a prince under a spell ...
der alte König (murmelt vor sich)
Ach, er liest wieder die Geschichte! (laut:) Mannomann, gehen wir lieber einkaufen!
Aha, he's readingthat story again! (out loud:) Man, let's go shopping instead!
Helpful hint: in a dictionary, irregular verbs are marked as irreg. They are usually listed in the back of the dictionary, with their irregular forms (some verbs are irregular in the past tense, but not in the present tense, etc.).