Chemistry: Chemistry the Central Science by Brown (I used the 11th edition). It is a pretty easy book to read from, not overly advanced, but not too easy either, just right for a person who wants to self-study and are new to the subject. Lots of problems per chapter, and a good amount of work out problems as well. But, if you want to have a good mastery over the material presented, buy the student solutions manual for the 11th edition as well. Costs about $55 on amazon + shipping for a new text, and about $19 + shipping for a used text.
Chemistry the Central Science covers all of general chemistry (most basic, i.e. learning how to manipulate units to get to the desired unit, all the way to an introduction into Organic chemistry)
For an advanced text in Chemistry: I read Linus Pauling's text which is pretty advanced, but I'd suggest buying, "Chemistry: The Quest for Insight (4th edition)" as reading two-three texts won't hurt you. Besides reading from multiple texts actually helps deepen the understanding in my experience.
Biology: For an introduction, I personally admire Campbell biology. Same thing as chemistry, but the focus here is knowing a lot of material. Usually you'll read from specific sections for a class, so it depends on what biology you'd be taking. But a good place to start is the genetics portion as the "chemistry of life" portion has some stuff taken from general chemistry that is used like valence electrons, etc... (chapter 8-9 in Central science). (You really don't need a solutions/study manual)
Covers the core areas as introductions, i.e. chemistry of life, cellular biology, genetics, ecology, evolution, etc...
Usually for advanced texts, you'd buy specific texts on the topic of interest.
For biology, you should also utilize further research (i.e., google etc) on topics that you don't get as some resources have links to sights that help with leading to better understanding. For me, I bought "genetics analysis and principles" by Robert J. Brooker, to help understand and increase my knowledge on genetics. It is a genetics based text so it is for the advanced student but it wasn't too advance in my opinion as I could understand it having never taken a course in genetics.
Mathematics: (I never took college Algebra and I didn't take precalculus either so I wouldn't be of much help to you in suggesting a book).
But when you do get to a level of taking Calculus, I personally would suggest Thomas/Finney 9th edition (has a light house on the cover) as your calculus text to self-study from. Great tool to grasp the fundamentals and not too watered down in my opinion, and he does use proofs which aides in the understanding in some sections. Like chemistry, I'd buy the solutions manuals in combination to help with learning.
(I know you didn't mention it..) As for physics, because you are going into medicine, I would lightly suggest reading "General Physics Sternheim and Kane", and the reason I am suggesting lightly is (1) that it costs a lot of money as the text isn't produced any longer, but I have it and from reading it, it incorporates more of the medical aspect to future medical students, and (2) some problems are wrong. IF you do end up buying it, you should definitely come here and ask in the home-work help section if a problem has you confused if it is right or wrong.
The MCAT, from my understanding, has only algebra based physics and not calculus based physics but I never read an algebra based physics text, so I wouldn't be good at suggesting one.
Another physics text I'd suggest is University Physics by Hugh. IT is a well paced book with a good amount of examples to help with further understanding but like always, search for more examples outside the text for mastery.
