KDP categories · Top KDP authors
O John Ma: Amazon KDP author data
As of Nov 6, 2026, O John Ma has 2 books on Amazon, 2 of them on a best-seller list in the last 30 days (best rank #4), mostly in Emergency Medicine, Allied Health Services, Emergency Medical Services.
| Median price | $166 |
|---|---|
| Price range (middle 50%) | $165 – $166 |
| Median reviews | 257 |
| Total reviews | 514 |
| New listings (30 days, incl. new editions) | 0 |
| Breakout books (30 days) | 0 |
What stands out
- Median price $166, 142% above the median of their main category, Emergency Medicine.
O John Ma's best-ranked books
-
Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th Edition
by O John Ma
- Price$167
- Rating4.8
- Reviews485
- Published2019-10
-
Ma and Mateers Emergency Ultrasound, Fourth Edition
by O John Ma
- Price$165
- Rating4.6
- Reviews29
Main categories
FAQ
How many books does O John Ma have on Amazon?
KDPTop tracks 2 of their books; 2 made an Amazon list in the last 30 days.
Which categories does O John Ma publish in?
Their books chart most often in Emergency Medicine, Allied Health Services, Emergency Medical Services.
How does O John Ma price their books?
The median price is $166; half of the books cost $165–$166.
Has O John Ma released new books recently?
0 new books in the last 30 days.
About this data
Data comes from KDPTop's daily crawl of Amazon's public Best Sellers pages; medians use the latest list. The opportunity score (0–100, higher is easier to enter) combines the review barrier, the share of low-review books, list turnover, new-release share and price.