I ran this as my first DMing experience and it was a ton of fun. The recommended 5 to 7 players is a lot but the adventure easily scales to lower party sizes. The Sci-Fi feel of Esper Genesis is really well represented in the Fall of Eos Keldor and it provides a great jumping off point for your own adventure path.

Esper Genesis is essentially D&D 5e with a sci-fi skin applied to it.

This free starter adventure requires the 5e rules to play. Most of the gameplay from 5e remains the same. Indeed, it seems like arcane spells (renamed channeling) and divine spells (renamed forging) remain almost the same, but with different names (e.g. Firebolt is now "force bolt"). Healing potions are now healing elixirs, etc. Weapons and Armor have close equivalents to their D&D counterparts. The authors explain that while future weapons would be far more deadly than their fantasy counterparts, but armor has also advanced as well, so instead of introducing a cumbersome "mega" damage or multiplier, they had just scaled them down to match each other for ease of play. It works. There are additional rules for modern weapons like shotguns (cone effect), spraying (burst) autofire, and recoil. It is all quite eloquent.

The re-skinning of the D&D rules makes it easy for anyone familiar with the 5e rule-set to jump right into the game. However, this starter book lacks some elements that one might expect in a sci-fi game (e.g. no mention of cybernetics, robotics, etc). The book also gives a brief taste of starship combat.

The majority of the book is a starter adventure "Fall of the Eos Keldor" which adequately shows off the new rules and flavor of the Esper Genesis universe. It has 4 pre-gen characters to quickly get you into the action (the equivalents of a Fighter, Rogue, Mage and Cleric). The adventure has a good mix of combat, investigation and star-ship battle.

Because this book seems to be a condensed or play-test version of the rules, it is not without its problems. For example, when playing through the adventure the 'Specialist' (rogue) wanted to pick up some of the guards weapons. While we know which fantasy weapons a 5e rogue has proficiency in, we were uncertain what the sci-fi equivalent would be from the weapon chart. Star-ship combat requires lots of rolls against a ship's "maneuver defense", yet that stat was not listed on the enemy's ship's stat block. And there were some blatant errors, like the channeling talent (spell) "Lightning Whip" which has a duration of 1 round, but the description clearly says "...for each of your turns for the duration..." (it probably should have a duration of 1 minute).