To consider the humble magnifying glass, in this or its level 0 form, one should keep in mind the way in which most act decks progress: the collection and spending of clues. Clues, barring a few tricks of a persuasion, or some exceptional luck, are found through successful investigation actions, using . And the magnifying glass provides a static +1 for those - and only those - actions. As such, it's a lovely card.
In its level 1 form, it costs 0 (a bargain!), can be played without spending an action because it's fast (double bargain!!) and boosts one of the core actions many investigators will be attempting (...triple bargain?!). While not as showy as some of the alternative clue-gathering techniques, such as those outlined above, or as potent as a Flashlight, which can reduce the shroud of some locations to 0, effectively ensuring success on any chaos token but , the magnifying glass is nonetheless reliable and inexhaustible - no charges, no uses, just steady +1 .
There's more: the upgraded version of this card comes with a which allows for quick pocketing of the glass. Given that it's free in resource- and action-cost to play, and then to return to hand, that's quite the boon. Why might one want to do that though? Perhaps hands are getting full and an investigator wants to bring out a gun, sword or book; perhaps there's a big test ahead, such as a parley action, in which you'd prefer to commit the magnifying glass for its icon; perhaps you're worried about being made to discard assets - there are plenty of such effects - and you'd rather hold on to the glass. More than anything else, it provides options: it may take up a hand slot, but it doesn't do so permanently, and if your investigator finds their role in the scenario shifting from combat to clues or vice versa, bingo, out/in comes the magnifying glass. Tip top.