Jake's Fantastic Journey

Jake's Fantastic Journey is a fantasy novel about a young boy's adventures, which start when he goes exploring another part of the garden. He comes across a gate with a strange stone head over it. Once he goes through that gate, his journey begins.
On this journey, he meets many strange beings-some human, some fantastical, and many alien beings. He eventually meets up with an alien being-Lok-who is of a similar age from a far-off planet, and their journey together begins.
Along the way, he loses his sister, Molly, when he visits his friend's planet.