Realistic: This is the most straightforward term, emphasizing that the events in the book are plausible and could occur in real life.
Relatable: This focuses on the reader's emotional connection to the story, implying that the characters and situations are familiar and resonate with their own experiences.
Authentic: This suggests that the book accurately portrays the realities of life, even if it doesn't explicitly claim to be based on true events.
Grounded: This emphasizes that the story is firmly rooted in the real world, without relying on fantasy or magical elements.
Possible: This simply indicates that the events depicted in the book are not impossible, even if they are unlikely.
Lifelike: This emphasizes the sense of verisimilitude in the story, making it feel as if it could be happening right now.
Factual: This term is typically used for non-fiction books, but can also be applied to fictional works that accurately depict historical events or scientific concepts.
Truthful: This suggests that the book is not simply believable, but also conveys a sense of honesty and integrity.
Ultimately, the best term to use depends on the specific book and the aspect you want to emphasize.