YES. TO. SQUARE. NECKLINES. It's been on the rise since about fall and is hitting full force this spring. Because this neckline is a classier one, I recommend sticking to classic colours like black and white, and let the neckline take the spotlight. This neckline can be casual or formal. For casual, a good way to create the illusion of this look without actually buying into it is to put a cardigan over a same coloured tube top (which has that straight across the chest look). This is the reason that black and white works because most of us have black or white tube tops and cardigans. Like the off the shoulder trend, this trend is likely to die out within a season, so I do not recommend investing in casual square neckline pieces.
However, when it comes to formal pieces with square necklines, such as dresses or jumpsuits, I recommend investing in a nice, ethically and sustainably made piece if you don't already have one. It's a classic and will always look beautiful for special occasions. Reformation, which is a sustainable fashion brand, carries gorgeous pieces with square necklines for reasonable prices. Also try vintage stores for classy square neckline dresses.