They can make it easier to remember. For example, if you know the origin of '人' (person) as a simple drawing of a person standing, it sticks in your mind better.
Well, kanji is vital. In light novels, it can enhance the aesthetic appeal. Readers who are familiar with kanji can quickly grasp the intended meaning. Moreover, kanji is often used for names of characters, places, and important items in the story. Without kanji, it would be difficult to create unique and memorable names, and the overall feel of the light novel would be less distinct.
There are several. Kanji for directions like 東 (higashi, 'east'), 西 (nishi, 'west'), 南 (minami,'south') and 北 (kita, 'north') can be used when describing a place or a journey. Kanji for numbers are also common. For example, 一 (ichi, 'one'), 二 (ni, 'two') etc. Also, kanji for colors such as 赤 (aka,'red') and 青 (ao, 'blue') are often found in light novels to describe characters' appearances or the scenery.
Yes, Esperanza Rising is considered historical fiction. It's set during a specific historical period and incorporates real-life events and circumstances.
Not always. Many manga have furigana (small hiragana or katakana above kanji) to help with pronunciation and understanding. Also, some simple manga are written mostly in hiragana and katakana.
In 'Esperanza Rising', the story is told from Esperanza's point of view. So, Esperanza is, in a sense, the one telling the story. We experience the events, the joys, and the sorrows through her eyes.