The Bunker Diary, by Kevin Brooks.

Teenager Linus Weems wakes up in an underground bunker (having been drugged with chloroform and kidnapped by a stranger). Linus is originally from a wealthy family, but since the death of his mother and subsequent arguments with his father, he had run away from school and been living on the streets. It's there that the stranger was able to kidnap Linus, by posing as a blind man needing assistance. As Linus adjusts to his new surroundings, he finds that the bunker has a kitchen, bathroom and six small bedrooms, but there are also cameras and microphones so that 'the man upstairs' (as Linus calls the kidnapper) can watch his every move.

Soon after Linus's arrival, other kidnap victims start being brought down via a lift- the lift being the means by which the kidnapper communicates. The first to arrive is nine-year-old Jenny, who forms a close bond with Linus. Jenny successfully convinces the kidnapper to send down food by presenting a polite, handwritten note to the camera. Soon after, other kidnap victims arrive, but have nothing in common with one another. Anja is a beautiful, smartly-dressed but somewhat selfish woman in her twenties, Bird is an older businessman who gets on well with Anja. There's also Fred- an addict, and Russell- an elderly man with a brain tumor. The group quickly learn that any attempt at escape results in 'punishments' from the kidnapper- such as deafening noise being played, being knocked out with gas and food deliveries stopping or being poisoned. At one point, the kidnapper sends down vodka and drugs- presumably to stop the group from trying to work together effectively. Linus tries to convince everyone to continue co-operating, but his efforts are merely met with hostility and complaints from some of the group.

Desperate for escape, Linus attempts to lure 'the man upstairs' into the bunker, but the kidnapper sends down a vicious Doberman in the lift instead. The dog savagely attacks Bird, but is then killed by Fred. Due to this latest escape attempt, the food stops, and Linus resorts to eating insects. Soon after this, the group receives some meat in the lift, and a note saying that whoever kills another will be freed, causing a descent into chaos.

The terminally-ill Russell tries to persuade Linus to gain his freedom by killing him or Bird (who's dying of his injuries from the dog-attack), but Linus refuses. Anja is then strangled to death by one of the group - the killer is never identified but is strongly presumed to be Bird, whose injuries are causing him to act strangely. The kidnapper continues to play games by sending a note down, falsely implying that Linus committed the murder to create suspicion. Fred then accidentally kills Bird in a fight, whilst trying to protect Jenny. Russell then commits suicide.

The days continue to pass and the remaining three are left hungry and cold. Eventually, the lift comes down with its doors closed, and doesn't go back up. The three realise that 'the man upstairs' has gone, though they do not know whether he has been killed or has simply abandoned them. The power shuts off, leaving them in darkness and without water. Now weakened and delirious, Fred is killed when he drinks some bleach, believing it to be water. Linus and Jenny are left alone.

Shortly after, Jenny dies in Linus's arms. He reports that she simply 'goes to sleep and doesn't wake up'. It is then implied that Linus also dies, as he writes that 'it doesn't hurt anymore', so he died. The book then abruptly finishes his diary mid-sentence. The identity and motivations of the kidnapper are left a mystery.

Quotes

Jenny smiled. ‘Why do we have two eyes?’ Russel plucked a loose button from his shirt and placed it on the bed about half metre from Jenny. Close one eye,’ he told her, ‘then touch the button with you finger.’ She closed one eye and reached out to touch the button. Her finder started wobbling, she frowned, then jabbed at the bed, missing the button by a couple of centimetres. ‘Hey,’ she said, opening her eye. Russell smiled. ‘That’s why we have two eyes, to stop us Heying.

Q:Why did the viper vipe ‘er nose ?

A: Because the adder ‘ad ‘er ‘ankerchief.

I remember plucking a rose thorn, licking it, and sticking it to my nose, making myself into a rhinoceros.

Budgies are bigger than grizzly bears

And crabs are covered in fleas

And parrots eat people and tigers eat pears

And bees make honey from cheese.

Slowworm rhinoceros tiger lion slug fox bear pigeon dog bear. No. Slowworm rhinoceros tiger lion slug fox bear pigeon dog. Is a slug an animal? slugdogslug. glug. A slug’s a whale in a jam jar. Hee. elephant whale insect mouse. what’s that funny thing? weasel cow badger fox. No. flop-eared rabbit weasel. hee. what’s the difference between a weasel and a stoat? a weasel’s weasly recognized and a stoat is stoatally different.

Buffaloes are hard to please

They don’t like mice and they don’t like peas

They only like to eat big things

Like mountain lions and eagles wings

But bumble bees on the other hand

Eat tiny things like ants and sand

And a million bee meals are so small

A baby buffalo could eat them all

I am here 32days, 768 hours, 46080 minutes, 2764800 seconds.