The London Eye Mystery has a plethora (overabundance) of words that a reader might not be familiar with. There are many in the first two chapters that are critical in establishing the setting and in developing the character of the narrator. For instance, the first and most critical part of the initial setting is the London Eye. It is called an observation wheel. This is term that is newly added to the English lexicon (vocabulary). This is a upgraded term for an elaborate Ferris Wheel that is built on a larger scale and has large capacity observation capsules for many people to ride in all at once instead of the the standard suspended bucket seats of an "old fashioned" Ferris Wheel. Observation: to notice or to perceive. Capsule: small compact enclosure.
The London Eye observation wheel is constructed with metallic hawsers. "Metallic" means that these "hawsers" are made of metal (a class of crystalline elementary substance). But what are "hawsers"? Hawser: heavy rope of cable for mooring or towing. The hawsers are metallic rope-like cables that facilitate the operation of the observation wheel. Another part of the observation wheel are the cantilevered structures: a rigid part of the structure horizontal to a vertical support that has tension on top and compression on bottom and is used for extended support.
From the second chapter, American readers learn of the English thing called "post" that comes to homes. Of course, the UK's post is the USA's mail. American English still has a vestige of the original noun for letters sent from person or entity to another in the terms post office, postman (not gender neutral), post box, postage stamp, and in expressions like "take it the the post" and "did you post that."
This gets you started on your way, and here are more words from chapters 1 and 2 that you can look up. Dictionary.com is a convenient and reliable online dictionary to use.