I am not too fond of the cover that is currently being used. I find it to be a bit bland and it isn't very attention grasping. Before the beginning of the story, you posted multiple options for covers, and I really like the third from the bottom! I feel that it fits the plot of the story and it is more appealing as a whole. However, the person on the cover doesn't seem to be the same age as the main character.
The title fits the story perfectly, and it is very right-to-the-point without giving too much information.
Chapter 1: "The small white door with a tiny window framed inside of it." This is an incomplete sentence. What about the small white door? Be sure to answer this question in order to make the sentence complete and easy to understand.
Chapter 1: "A needle is then plunged into my neck, and a green liquid is injected under my skin." This sentence is written in present tense and the rest of the flashback/experience is written in past tense. Be sure to keep this consistent throughout the story, as it can be confusing to your readers if the tense suddenly changes.
Chapter 2: "'What is it.' The boy asks anxiously." Here, there should be a question mark after "What is it," since the character asked a question.
Some words and/or explanations are overused in certain places throughout the story. For example, in the first paragraph of Chapter 1, you explain how everything is white. Although you clearly describe the setting, you describe each aspect of the setting individually, which makes the descriptions seem plain and dragged-on. Instead of individually explaining each thing that is white, perhaps you could begin by writing "I open my eyes and I am surrounded by a sea of white," (or something of the sort) and then proceed to describe the room in one or two sentences. By using the character's viewpoint and personality to describe the setting, the audience would be able to understand how the character thinks while simultaneously being able to imagine the setting. Without more thorough descriptions, the story is more told rather than shown, which may cause readers to lose interest. Be sure to describe the character's thoughts in addition to the story's events.
The chapters are each perfect lengths, and very easy to read through. I do feel that you could elaborate a bit more on your explanations and expand the chapters that way. Despite this, the chapters contain a perfect amount of action and they end on suspenseful cliffhangers that bring the audience into the rest of the story.
However, I did feel that the plot moved a bit quickly. Perhaps you could have lengthened the build-up in Chapter 1. The audience wants to have a sense of how Eric feels when he realizes that he can't remember anything. The story moves along quite quickly, so you may want to lengthen out some scenes in order to build up more suspense.
The characters overall seem a bit bland. The story is primarily described through the actions of the character and through dialogue. I feel that the story would be much more lively if you added some details and more personality to your characters. You should incorporate what they are thinking, how they are feeling, etc. instead of just describing the scene. You may want to consider adding some additional sensory details into the story so that the audience can clearly imagine the setting throughout.
Overall, I thought the plot of the story was very creative and you added some interesting flashbacks and foreshadowing into your writing. I feel that some additional build-up is necessary in your first few chapters, and you could use some more details to describe the setting and the characters.