For beginners, 'The Hitchhiker's Guide to the Galaxy' is a great start. It's easy to read and really funny. You'll get introduced to all kinds of crazy science - fiction concepts in a light - hearted way. Another good one is 'Ender's Game'. The story is very engaging and it doesn't require a lot of prior knowledge of the science - fiction genre. It focuses on a relatable character, Ender, and his journey. 'Ready Player One' by Ernest Cline is also a good pick. It has a lot of pop - culture references that are fun to pick up on, and it's set in a really interesting virtual world.
I would recommend 'I, Robot' by Isaac Asimov. It's a collection of short stories that are easy to follow and they introduce some really important science - fiction ideas like robotics and artificial intelligence. 'A Wrinkle in Time' by Madeleine L'Engle is also suitable for beginners. It has a bit of a fantastical element combined with science - fiction concepts like time travel. It's a story about a young girl's journey through different dimensions to save her father. 'The Time Machine' by H.G. Wells is a classic that's not too difficult to understand. It's one of the first science - fiction stories about time travel and it can give beginners a good sense of the genre's potential.