Before I start, I'll just say here that textbooks are only useful if you actually plan on using them. Having said that, spoon3er is right and you'll find an anatomy, physiol, path and histo book especially useful. The ones on the official list are:
- Moore & Dalley: Clinically Oriented Anatomy
- Kumar, Cotran & Robbins: Robbins Basic Pathology
- Boron & Boulpaep: Medical Physiology
- Junqueira & Carneiro: Basic Histology
In addition to the Moore, you might find an anatomy atlas useful. Atlases don't have explanations, but they have awesome pictures.
- Netter: Atlas of Human Anatomy (pretty painted colour-coded pictures)
- Rohen, Yokochi & some guy starting with L: Color Atlas of Anatomy (PHOTOS... sexiest anatomy book of all time).
If you want to spend more, instead of the baby Robbins above, Robbins Pathological Basis of Disease might be a good investment.
Boron's physiol is a bitch to read. My advice: AVOID IT. I bought one and I'm only keeping it out of spite. Buy a Guyton instead. I've also heard good things about Sherwood, but can't say anything from personal experience.
Histology is useful, but not necessary. There are enough histo resources on the web.
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At some point during first year, you'll also want
Larsen: Human Embryology
(oh God I hate I hate I hate embryol... This textbook is really hard and boring but I think it's because embryol is hard and boring... If anyone has any better suggestions I'm open here.)
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If you did not do biology in high school, Campbell & Reece's Biology is a real lifesaver. Totally awesome explanations of genetics, cell cycle, and some basic biochem. But know that you're also paying for 600 pages of non-human biology, i.e. stuff like the mosquito life cycle.
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Epstein et al: Clinical Examination.
I wish I had used this more. You'll want this.
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Those are the only ones I'd really recommend you to pay money for. I've also got a microbiology, a pharmacology, a neuro and a biochem but you'll either find that 1) you dont need to use them very often, or 2) you need them more in 2nd year.
Hope that helps, and make sure you go to medcamp.