For out-of-print volumes, check eBay , but be aware that some early Deluxe volumes can be expensive.
If you just want to read the story, the Compendiums are the most cost-effective way to get the content, though they use standard paperback paper. Tips for Collectors
These are standard-sized hardcovers (larger than a trade paperback but smaller than the Deluxe) and collect about 12 issues each. Where to Buy
When buying high-quality paper editions, look for descriptions like "New" or "Near Mint" (NM) to ensure the paper hasn't been damaged by moisture or rough handling.
If buying original individual issues, " Newsstand " editions are often considered more valuable by collectors due to lower survival rates in high grades.