Although not a basic item, Sorcerer's Shoes is the item from which the flat magic penetration gold value is derived. From this item derives a value of aproximately 34.33 gold per point of magic penetration.
In contrast, Sorcerer's Shoes is less effective for non-offensive casters such as supports or tanks, as their typically low magic damage stats prevent the item from receiving its full value, compared to the higher damage results of a Carry. One of the two defensive boots would likely be a better pick, as the added survivability will be of more value to these roles.
These boots are less efficient against enemies with high magic resistance. However, they synergize well with other magic penetration items, percentage items such as Void Staff in particular.
It is possible to sell these boots at late-game once you have Void Staff or other magic penetration items such as Liandry's Torment, as the extra magic penetration is arguably negligible.
It's usually recommended then to buy Ionian Boots of Lucidity as most users of Sorcerer's Shoes work well with cooldown reduction. However, depending from the champion you are using or the enemies you are facing, you may want to buy other types of boots, such as Mercury's Treads (due to the tenacity).
For nearly a century, the greatest mage in Valoran resided in the scorched desert of the Zear realm until the first crusade of the Rune Wars devastated the entire region forcing millions to flee. The crusaders killed all desperate travelers attempting the mass exodus from Zear, but one mage escaped their grasp by making such haste across the land that word spread throughout Valoran that the very shoes this mage wore must be imbued with immense power.