A bored and lonely child picks up a red colouring stick and draws a small door on her bedroom wall – then walks through it into a luminous forest lit with blue Chinese lanterns, golden strings of fairy lights and numerous fireflies. Running through the forest is a stream. So, using her red crayon, the girl draws herself a boat and climbs in. Gradually she drifts into the watery highway of a vast and complex castle, peopled with fierce guards. As she makes her escape difficulties beset her, but she cleverly draws a solution to overcome each challenge. Eventually the girl rescues an exotic purple bird that guides her through another small door, which leads her back into her home city.

Both the idea of a portal into another world and the concept of a ‘magic pencil’, where a drawn object becomes ‘real’, are familiar ones in children’s literature. For the former, think Carroll’s Alice in Wonderland (1865), Lewis’s The Lion, the Witch and the Wardrobe (1950) and Pullman’s Northern Lights (1995). For the latter, think Harold and the Purple Crayon (1955) by Crockett Johnson, as well as Magpie Magic (1999) by April Wilson and Chalk (2010) by Bill Thomson – two titles which, like this book, are wordless picturebooks. The portal is a literary device that is often used to link real and imagined worlds, while the magic pencil enables an illustrator to demonstrate visually their ability to adapt and control an invented space using their own interventions.

In Journey, Aaron Becker has created a wonderfully complex fantasy world that draws on a range of geographical and cultural references. On his website, Becker says he was inspired by a castle in France, a neighbourhood in Washington DC and a village in Germany, but also contained within the images are Italianate domes and Venetian gondolas; Roman viaducts and Middle Eastern walled cities; Far Eastern curved roofs and medieval turreted towers. There is an element of the steampunk aesthetic, especially in the myriad locks, bridges, ships, hot air balloons and strange Jules Verne-like flying machines that populate this world, as well as in the many smaller mechanical devices that involve pulleys, wheels, cogs, and levers. Great care is taken over tiny details, such as those of the costumes, including the guards’ uniforms, knights’ helmets and ladies’ fringed umbrellas. Be prepared to pore over these illustrations for hours.

Becker, an American artist who formerly worked in the film industry, wanted his book to be highly detailed, but he explains that: ‘Nothing is complicated. It’s just a bunch of little things that add up to being complicated. So this big drawing of a castle is just made up of one shape, after another shape, after another shape – squares, circles, domes, triangle, arches.’ He used watercolour for the illustrations as it ‘felt like the right medium to give it [the book] a dreamy feeling’, printing his pencil drawing onto watercolour paper, using watercolour washes and tracing lines with acrylic ink. The way Becker uses colour adds extra depth to the book. For instance you can be surprised by a page drenched in shades of verdant greens, or warm oranges and purples. Murkier colours are used for the castle, but even these are enriched by shiny slate-greys and sparkling gold.

There’s a real sense of adventure in this book as the protagonist heads into the unknown and has to call on her own bravery and strength in the face of danger. On her journey she learns about freedom and compassion. And when she returns she discovers what was already there on her doorstep – a friend who, like her, loves to draw. She is lonely no longer. Like the imaginary world it depicts, there are many layers to this beautiful, thoughtful book.

Journey was a Caldecott Honor book for 2014. Becker has created two subsequent wordless picturebooks, Quest (2014) and Return (2016), and together the three form the Journey trilogy.