What book is good to use in assessing medical criteria for admitting a patient in the hospital as an inpatient?

Your doctor: There is probably not an adequate printed resource that will outline admision criteria. This is something best done by meeting with your primary care physician or a consultant who uses clinical judgement that they get from thier training, experience, clinical practice guidelines, and hospital specific admission criteria. There may also be controls or policies from your insurance company on this.

Milliman guidelines: Many use the milliman criteria.