Steam API
Steam (steampowered.com) has 5 public methods: get game details, get player count history, list most played games, list top sellers and get game reviews. Each costs 1 credit per completed run (1¢ with pay as you go); failed runs are free.
Unofficial. Not affiliated with or endorsed by Steam.
Methods
5Finds a PC game on Steam by name, store link or app ID and returns its store details, country price, reviews, tags and live player count.
Returns name, price in the chosen country, reviews, tags, platforms, requirements, players online
Readstore.steampowered.com/get_gameGets a Steam game's current players, 24-hour peak, all-time peak and monthly player-count history from SteamCharts. Takes a game name, SteamCharts or Steam store link, or Steam app ID.
Returns current players, 24-hour peak, all-time peak and date, monthly average and peak players
Readstore.steampowered.com/get_player_count_historyLists the games with the most players on Steam right now, with current and peak players and prices for a chosen country.
Returns rank, game name, players now, peak today, price, currency, link, app id
Readstore.steampowered.com/list_most_playedLists Steam's top-selling, discounted, or new and trending games in store order, with prices for a chosen country, review summaries and release dates.
Returns rank, game name, current and original price, currency, discount, review summary, release date, Steam link, app id
Readstore.steampowered.com/list_top_sellersReads public Steam player reviews for a game by name, store link, or app ID, with optional sorting (most helpful or most recent), verdict and language filters. Overall figures cover all lifetime reviews in every language and verdict.
Returns game title and link, overall review summary, percent positive, total reviews, reviews (ID, link, recommended, text, posted date, hours played, helpful and funny votes)
Readstore.steampowered.com/get_game_reviews