Learn Finnish: Tykkäätkö sinä historiasta?

This is because of the verb tykätä (to like). In Finnish, verbs often demand that the words attached to them take a specific case ending (a concept known as "verb rection"). Both tykätä and pitää (which also means "to like") require the thing you like to be in the elative case, which means adding -sta or -stä.

Why are there two ks in tykkäätkö when the dictionary form is tykätä?

Tykätä is a type 4 verb (ending in -tV, where V is a vowel). These verbs undergo "reverse consonant gradation". This means the dictionary form has the "weak" consonant (one k), but when you form the stem to conjugate it, the consonant strengthens to the "strong" grade (two ks). This gives us the stem tykkää- before we add the -t and -kö endings.

Why is the question particle -kö instead of -ko?

This is a great example of vowel harmony! The stem of the verb is tykkää-. Because it contains the front vowel ä, any endings attached to that word must also use front vowels (ä, ö, or y). Therefore, we use the front-vowel version of the question particle, -kö.

Is it necessary to include the word here?